Display Device and Method for Manufacturing Display Device

ABSTRACT

The thickness of a display device including a touch sensor is reduced. Alternatively, the thickness of a display device having high display quality is reduced. Alternatively, a method for manufacturing a display device with high mass productivity is provided. Alternatively, a display device having high reliability is provided. Stacked substrates in each of which a sufficiently thin substrate and a relatively thick support substrate are stacked are used as substrates. One surface of the thin substrate of one of the stacked substrates is provided with a layer including a touch sensor, and one surface of the thin substrate of the other stacked substrate is provided with a layer including a display element. After the two stacked substrates are attacked to each other so that the touch sensor and the display element face each other, the support substrate and the thin substrate of each stacked substrate are separated from each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One embodiment of the present invention relates to a display device fordisplaying an image.

2. Description of the Related Art

A variety of portable electronic devices, such as a cell phone, asmartphone, a personal computer, a tablet terminal, a portable gamemachine, and a portable music player, have recently come into widespreaduse. More intuitively operable electronic devices can be obtained byproviding a touch sensor over a display portion for image display as aninterface of such portable electronic devices.

In the display portion, a light-emitting device including an organicelectroluminescent (EL) element, a liquid crystal display device, anelectronic paper performing display by an electrophoretic method, or thelike can be typically used.

For example, in a basic structure of an organic EL element, a layercontaining a light-emitting organic compound is provided between a pairof electrodes. By applying voltage to this element, light emission fromthe light-emitting organic compound can be obtained. A display deviceincluding such an organic EL element needs no backlight which isnecessary for liquid crystal display devices and the like; therefore,thin, lightweight, high contrast, and low power consumption displaydevices can be obtained. For example, Patent Document 1 discloses anexample of a display device including an organic EL element.

Typical touch sensors are of resistive type and of capacitive type;besides, a variety of types such as a surface acoustic wave type and aninfrared type are known.

REFERENCE

-   [Patent Document 1] Japanese Published Patent Application No.    2002-324673

SUMMARY OF THE INVENTION

It is desirable that portable electronic devices be lighter, smaller,and thinner for higher portability and convenience. This requires thateach component of electronic devices be thinner and smaller. One exampleof components of electronic devices is a display device.

In the case of a display device in which a touch sensor and a displayportion are stacked, it has been difficult to reduce its total thicknesssufficiently. Although it is possible to reduce the thickness of thedisplay device by, for example, forming a touch sensor and a displayelement over respective relatively thick substrates at the time ofmanufacturing the touch sensor and the display portion and then bypolishing the back sides of the substrates, the polishing step aftermanufacturing the elements causes a decrease in yield. In the case offorming the elements directly over thin substrates, the deflection ofthe substrates is large, and it is difficult to transport thesubstrates. In addition, there arise problems such as breakage of thesubstrates in transporting or processing the substrates.

In some cases, a substrate provided with a color filter is located so asto overlap with a display element to obtain a display device with highdisplay quality. In the case of using a thin substrate as thatsubstrate, there have been problems of difficulty in overlapping thecolor filter and the display element with high alignment accuracy due tothe aforementioned deflection of the substrate or the like, anddifficulty in achieving both a high display quality and a smallthickness of the display device.

The present invention was made in view of the foregoing technicalbackground. An object is to reduce the thickness of a display deviceincluding a touch sensor. Another object is to reduce the thickness of adisplay device with high display quality. Another object is to provide amethod for manufacturing a display device with high mass productivity.Another object is to provide a display device with high reliability.

In order to achieve the above object, a focus is placed on the structureof substrates used to manufacture a touch sensor and a display element.Stacked substrates in each of which a sufficiently thin substrate and arelatively thick support substrate are stacked are used as thesubstrates. One surface of the thin substrate of one of the stackedsubstrates is provided with a layer including a touch sensor, and onesurface of the thin substrate of the other stacked substrate is providedwith a layer including a display element. After the two stackedsubstrates are attacked to each other so that the touch sensor and thedisplay element face each other, the support substrate and the thinsubstrate of each stacked substrate are separated from each other.

That is, a method for manufacturing a display device in one embodimentof the present invention includes the steps of: attaching a firstsubstrate, which is fixed to a first support substrate and provided withan element layer including a light-emitting element over a surface notfacing the first support substrate, and a third substrate, which isfixed to a third support substrate and provided with a color filterlayer over a surface not facing the third support substrate, to eachother with a first adhesive layer so that the element layer and thecolor filter layer face each other, and then separating the thirdsubstrate and the third support substrate from each other; attaching thethird substrate and a second substrate, which is fixed to a secondsupport substrate and provided with a sensor layer over a surface notfacing the second support substrate, to each other with a secondadhesive layer so that the element layer and the sensor layer face eachother, and then separating the second substrate and the second supportsubstrate from each other and separating the first substrate and thefirst support substrate from each other. In addition, a glass substratehaving a thickness of 10 μm to 200 μm is used as each of the first tothird substrates, and a base substrate thicker than the glass substrateis used as each of the first to third support substrates.

With the use of such a manufacturing method, a display device includinga touch sensor and having a very small total thickness can bemanufactured with high yield. In addition, the second substrate providedwith the sensor layer and the first substrate provided with a displayelement can be attached to each other with high alignment accuracybecause the two substrates are provided with the respective supportsubstrates.

Furthermore, the three substrates provided with the touch sensor, thedisplay element, and the color filter layer, respectively, are stacked.Accordingly, a display device having a sufficiently small totalthickness and a high display quality can be manufactured with highyield. When the third substrate provided with the color filter layer andthe first substrate provided with the display element are attached toeach other, the substrates are provided with the respective supportsubstrates. Thus, misalignment of color filters and pixels can besuppressed, and the two substrates can be attached to each other withhigh alignment accuracy. Thus, it is possible to obtain a display devicehaving a very high pixel resolution (e.g., 300 ppi or higher, preferably400 ppi or higher, and more preferably 500 ppi or higher) and having avery small total thickness.

A method for manufacturing a display device in another embodiment of thepresent invention includes the steps of: attaching a first substrate,which is fixed to a first support substrate and provided with an elementlayer including a light-emitting element over a surface not facing thefirst support substrate, and a third substrate, which is fixed to athird support substrate and provided with a color filter layer over asurface not facing the third support substrate, to each other with afirst adhesive layer so that the element layer and the color filterlayer face each other, and then separating the third substrate and thethird support substrate from each other; attaching the first substrateand a second substrate, which is fixed to a second support substrate andprovided with a sensor layer over a surface not facing the secondsupport substrate, to each other with a second adhesive layer so thatthe color filter layer and the sensor layer face each other, and thenseparating the second substrate and the second support substrate fromeach other and separating the first substrate and the first supportsubstrate from each other. In addition, a glass substrate having athickness of 10 μm to 200 μm is used as each of the first to thirdsubstrates, and a base substrate thicker than the glass substrate isused as each of the first to third support substrates.

With the use of such a manufacturing method, a display device providedwith a touch sensor on a side opposite to a display side of the displaydevice and having a small total thickness can be manufactured with highyield. Since the touch sensor is provided on the side opposite to thedisplay side, an input operation can be performed without displayobscured by a user's finger or the like, which is suitable for anelectronic device capable of running game content involving a touchinput or playing video content such as a movie.

A method for manufacturing a display device in another embodiment of thepresent invention includes the steps of: attaching a first substrate,which is fixed to a first support substrate and provided with an elementlayer including a light-emitting element over a surface not facing thefirst support substrate, and a second substrate, which is fixed to asecond support substrate and provided with a stack of a sensor layer anda color filter layer over a surface not facing the second supportsubstrate, to each other with an adhesive layer so that the elementlayer and the sensor layer face each other; and separating the firstsubstrate and the first support substrate from each other and separatingthe second substrate and the second support substrate from each otherafter attaching the first substrate and the second substrate to eachother. In addition, a glass substrate having a thickness of 10 μm to 200μm is used as each of the first and second substrates, and a basesubstrate thicker than the glass substrate is used as each of the firstand second support substrates.

With the use of such a manufacturing method, a touch sensor and a colorfilter can be stacked over one substrate; thus, the number of substratescan be reduced and the display device can have a smaller totalthickness. When the substrate and a substrate provided with a displayelement are attached to each other, the substrates are provided withrespective support substrates. Accordingly, the two substrates can beattached to each other with high alignment accuracy, and the displaydevice can have a high pixel resolution.

In the above embodiment, it is preferable that the glass substrate befixed to the base substrate by being in close contact with each otherand that an attachment surface of each of the glass substrate and thebase substrate has a surface roughness of 2 nm or less.

Alternatively, in the above embodiment, it is preferable that the basesubstrate be provided with a resin containing an organic compound or asilicon compound and that the glass substrate be fixed to the basesubstrate by close contact between the resin and the glass substrate.

With the use of such a stacked substrate, the support substrate and thesubstrate can be prevented from being separated from each other duringthe steps of manufacturing a display element, a touch sensor, a colorfilter, and the like, and can be easily separated during the separationstep.

A display device in one embodiment of the present invention includes afirst substrate, which is provided with an element layer including alight-emitting element, and a second substrate, which is provided with asensor layer. The first substrate and the second substrate are attachedto each other with an adhesive layer so that the element layer and thesensor layer face each other. In addition, each of the first and secondsubstrates is a glass substrate having a thickness of 10 μm to 200 μM.Furthermore, a first conductive film is provided over the firstsubstrate, a second conductive film electrically connected to the sensorlayer is provided over the second substrate, and the first conductivefilm and the second conductive film are electrically connected to eachother through a conductive connector.

With such a structure, a display device including a touch sensor canhave a very small total thickness. When an external connection electrodeconnected to an FPC or the like for exchanging signals with the touchsensor is provided on the side of the substrate where a display elementis formed, both the external connection electrode for the touch sensorand an external connection electrode for a display portion including thedisplay element can be provided on one surface side of the displaydevice. Thus, the area necessary for connection of the FPC can bereduced. When such a display device is applied to an electronic device,the area occupied by the display device in the electronic device can bereduced and the electronic device can therefore be designed more freely.

In the display device, it is preferable that the second substrate beprovided with a color filter layer stacked over the sensor layer.

When the substrate provided with the touch sensor is also provided withthe color filter in the above manner, the color filter can be providedwith little increase in thickness. Thus, it is possible to obtain adisplay device having a very small total thickness and a high displayquality.

In the above display device, it is preferable that the adhesive layer beprovided between the connector and the light-emitting element so as tosurround the light-emitting element, and that the first conductive filmand the second conductive film be electrically connected to each otheroutside a region surrounded by the adhesive layer.

When the adhesive layer is provided so as to surround the light-emittingelement and a connection portion of the touch sensor is provided in aregion outside the adhesive layer in the above manner, impurities inmembers including the connector provided in the connection portion canbe prevented from entering a region where the light-emitting element isprovided, whereby the display device can have high reliability.

In any of the above display devices, it is preferable that the adhesivelayer contain a glass material.

For the adhesive layer, a material containing a glass material, such asa glass body formed by melting and solidifying powder glass (also calledfrit glass), is used. Such a material can effectively suppresspermeation of moisture and gas and can therefore suppress thedeterioration of the light-emitting element. Thus, the display devicecan have very high reliability.

In any of the above display devices, it is preferable that the elementlayer include a transistor electrically connected to the light-emittingelement, and that an oxide semiconductor be used as a semiconductorwhere a channel is formed in the transistor.

A transistor formed using an oxide semiconductor is preferable becauseit can achieve high field-effect mobility with relative ease and cantherefore have a smaller size than a transistor formed using amorphoussilicon, for example, and increases in aperture ratio and resolution canbe achieved. In some cases, an oxide semiconductor may change itselectrical characteristics due to an impurity such as moisture. Thus, byproviding a transistor inside the adhesive layer or using a materialcontaining a glass material for the adhesive layer as described above,the display device can have higher reliability.

In any of the above display devices, it is preferable that a firstconnection terminal electrically connected to the element layer and asecond connection terminal electrically connected to the firstconductive film be provided over the first substrate so as not tooverlap with the second substrate, that at least one FPC be electricallyconnected to each of the first and second connection terminals, and thata reinforcing material be provided in contact with the FPC and thesecond substrate.

When a region between the FPC and the second substrate is reinforcedwith the reinforcing material in the above manner, it is possible toprevent even a very thin substrate from being broken in the mechanicallyrelatively weak region in later handling. Thus, the display device canhave very high reliability.

Note that in this specification, a display device refers to an imagedisplay device provided with a plurality of pixels. In addition, thedisplay device includes all the following modules: a module in which aconnector, such as a flexible printed circuit (FPC) or a tape carrierpackage (TCP), is attached to a display device; a module in which aprinted wiring board is provided at the end of a TCP; and a module inwhich an integrated circuit (IC) is directly mounted by a chip-on-glass(COG) method on a substrate where pixels are formed.

According to the present invention, the thickness of a display deviceincluding a touch sensor can be reduced. Alternatively, the thickness ofa display device having high display quality can be reduced.Alternatively, a display device can be manufactured with high massproductivity. Alternatively, a display device having high reliabilitycan be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1E illustrate an example of a method for manufacturing adisplay device in one embodiment of the present invention.

FIGS. 2A to 2D illustrate an example of a method for manufacturing adisplay device in one embodiment of the present invention.

FIGS. 3A to 3C illustrate an example of a method for manufacturing adisplay device in one embodiment of the present invention.

FIGS. 4A to 4D illustrate an example of a method for manufacturing adisplay device in one embodiment of the present invention.

FIGS. 5A and 5B illustrate a configuration example of a display devicein one embodiment of the present invention.

FIG. 6 illustrates a configuration example of a display device in oneembodiment of the present invention.

FIG. 7 illustrates a configuration example of a display device in oneembodiment of the present invention.

FIGS. 8A to 8E each illustrate a configuration example of alight-emitting element in one embodiment of the present invention.

FIGS. 9A to 9D each illustrate an example of an electronic deviceincluding a display device in one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described with reference to drawings. Note that thepresent invention is not limited to the following description, and it iseasily understood by those skilled in the art that various changes andmodifications can be made without departing from the spirit and scope ofthe present invention. Therefore, the present invention should not beconstrued as being limited to the description in the followingembodiments. Note that in the structures of the invention describedbelow, the same portions or portions having similar functions aredenoted by the same reference numerals in different drawings, anddescription of such portions is not repeated.

Note that in each drawing described in this specification, the size, thelayer thickness, or the region of each component is exaggerated forclarity in some cases. Therefore, embodiments of the present inventionare not necessarily limited to such scales.

Note that the term “electrically connected” in this specification andthe like includes the case where components are connected through an“object having any electric function”. There is no particular limitationon an object having any electric function as long as electric signalscan be transmitted and received between components that are connectedthrough the object. Examples of an “object having any electric function”are a switching element such as a transistor, a resistor, a coil, acapacitor, and elements with a variety of functions as well as anelectrode and a wiring.

Embodiment 1

In this embodiment, a configuration example of a display device in oneembodiment of the present invention and an example of a manufacturingmethod thereof will be described with reference to drawings.

[Manufacturing Method Example 1]

First, a stacked substrate in which a first substrate 101 is stackedover a first support substrate 102 is prepared.

As the first substrate 101, a substrate having an insulating surface andhaving a thickness of 10 μm to 200 μm is used. As a material of thefirst substrate 101, a glass material, an organic resin material, aconductive material containing a metal or an alloy, or the like can beused.

It is preferable to use a glass material for the first substrate 101.With the glass material, a large-sized substrate having an extremelyflat surface and a uniform thickness can be manufactured with relativeease. Such a glass substrate can be manufactured using a float method,an overflow method, or the like.

In the case where the first substrate 101 is on a display surface side,a light-transmitting substrate is used. On the other hand, in the casewhere the first substrate 101 is on a side opposite to the displaysurface, a non-light-transmitting substrate may be used. Sinceconductive materials generally have high thermal conductivity, when aconductive substrate is used as the first substrate, for example, it ispossible to promote dissipation of heat generated when an element in anelement layer 103 which is described later is driven. In the case ofusing a conductive substrate, a surface where the element layer 103 isto be formed is preferably subjected to insulating treatment.

As the first support substrate 102, a base substrate which is thickerthan at least the first substrate 101 is used. The thickness of thefirst support substrate 102 is preferably determined in consideration ofthe thickness of the first substrate 101 so that the substrate can betransported easily at the time of manufacturing the element layer 103which is described later. For example, the total thickness of a stack ofthe first support substrate 102 and the first substrate 101 may be setsubstantially equal to the thickness of a substrate which can beprocessed in an existing apparatus line (or production line ormanufacturing line). Specifically, the thickness of the supportsubstrate is set such that the total thickness of the first supportsubstrate 102 and the first substrate 101 (also an adhesive when used)is larger than 0.4 mm and less than or equal to 2.0 mm, preferablylarger than or equal to 0.5 mm and less than or equal to 1.0 mm.

As a material of the first support substrate 102, a glass material, anorganic resin material, a conductive material containing a metal or analloy, or the like can be used. A glass material is preferably used.With the use of a glass material, the flatness of an attachment surfacefor the first substrate 101 can be increased, and the adhesion betweenthese substrates can be increased.

The first support substrate 102 and the first substrate 101 are fixed toeach other by being in close contact with each other or by using anadhesive capable of allowing separation. Therefore, unintentionalseparation can be prevented in the steps of manufacturing the elementlayer 103, and separation can be caused easily in a later separationstep.

In the case where the first support substrate 102 and the firstsubstrate 101 are fixed by being in close contact with each other, theattachment surface of each substrate should have an arithmetic meansurface roughness of 5 nm or less, preferably 2 nm or less. By closecontact between two surfaces having such an extremely high flatness, thefirst support substrate 102 and the first substrate 101 can be fixed toeach other.

The first substrate 101 and the first support substrate 102 can beseparated from each other by applying physical force in a directionperpendicular to the attachment surfaces. Here, separation can be easilycaused when a region having a relatively large surface roughness isprovided at an end portion of either of the substrates which serves as astarting point of separation.

In the case where the first support substrate 102 and the firstsubstrate 101 are fixed to each other by using an adhesive capable ofallowing separation, a resin containing an organic compound or a siliconcompound is preferably used as the adhesive. In the case of using aglass material for the first support substrate 102 and the firstsubstrate 101, it is particularly preferable to use a resin having asiloxane bond.

The first support substrate 102 and the first substrate 101 are fixed toeach other in such a manner that a resin diluted with a solvent isapplied to the first support substrate 102, the resin is cured byvaporizing the solvent, and then the first substrate 101 is placed inclose contact with and pressed against the resin. The first supportsubstrate 102 and the first substrate 101 can be easily separated fromeach other by applying force in a direction perpendicular to theattachment surfaces. By forming the resin on the first support substrate102 side in the above-described manner, the resin can be prevented fromremaining on the first substrate 101 after the separation.

In this embodiment, glass substrates are used as the first supportsubstrate 102 and the first substrate 101.

Next, the element layer 103 is formed over a surface of the firstsubstrate 101 on a side opposite to the first support substrate 102(FIG. 1A).

The element layer 103 includes a plurality of pixels each including atleast a display element. In the case of an active-matrix display device,the pixels may each include a transistor and a capacitor. The elementlayer 103 may also be provided with a driver circuit for driving thepixels (such as a gate driver circuit or a source driver circuit). Theelement layer 103 further includes a wiring and an electrode.

As the display element, an organic EL element, a liquid crystal element,a display element employing an electrophoretic method, or the like canbe used.

The element layer 103 can be manufactured by a variety of manufacturingmethods. For example, in the case of an active-matrix display deviceincluding an organic EL element, a gate electrode (and a wiring), a gateinsulating layer, a semiconductor layer, and a source electrode and adrain electrode (and wirings) which form a transistor are provided overthe first substrate 101, and a light-emitting element electricallyconnected to the transistor is formed thereover with an insulating layerprovided therebetween, by stacking a first electrode, a layer containinga light-emitting organic compound, and a second electrode in this order.

Then, a stacked substrate in which a second substrate 111 is fixed ontoa second support substrate 112 is prepared. Here, as the stackedsubstrate, the one that is similar to that described above can be used.

Next, a sensor layer 113 is formed over a surface of the secondsubstrate 111 on a side opposite to the second support substrate 112(FIG. 1B). Here, the case of using a projected capacitive touch sensoras a sensor element in the sensor layer 113 will be described.

The sensor layer 113 includes a first sensor electrode 114, a secondsensor electrode 115, and an insulating layer 116 which insulates thefirst sensor electrode 114 and the second sensor electrode 115 from eachother. The first sensor electrode 114 is provided in the form of stripesin one direction. The second sensor electrode 115 is provided in theform of stripes intersecting the first sensor electrode 114. The firstsensor electrode 114 and the second sensor electrode 115 do notnecessarily intersect orthogonally and may form an angle of less than90°.

The insulating layer 116 is provided so as to be sandwiched between thefirst sensor electrode 114 and the second sensor electrode 115 in orderto insulate the two electrodes from each other. FIG. 1B illustrates astructure in which the insulating layer 116 is provided so as to coverthe first sensor electrode 114, but the insulating layer 116 may beprovided only in portions where the first sensor electrode 114 and thesecond sensor electrode 115 intersect each other.

In the case where the sensor layer 113 is provided on a display surfaceside, a light-transmitting conductive material is preferably used forthe first sensor electrode 114 and the second sensor electrode 115. Inaddition, a light-transmitting insulating material is preferably usedfor the insulating layer 116.

Note that there is no limitation on the order of formation of theelement layer 103 and the sensor layer 113, which may be formedseparately.

Next, the stacked substrate of the first support substrate 102 and thefirst substrate 101 and the stacked substrate of the second supportsubstrate 112 and the second substrate 111 are arranged so that theelement layer 103 and the sensor layer 113 face each other, and thefirst substrate 101 and the second substrate 111 are attached to eachother with an adhesive layer 104 (FIG. 1C).

For the adhesive layer 104, a curable resin such as a heat curableresin, a photocurable resin, or a two-component type curable resin canbe used. The resin is applied to the first substrate 101 or the secondsubstrate 111, and the resin is cured in a state where the firstsubstrate 101 and the second substrate 111 are in close contact with theresin, whereby the two substrates can be attached to each other.

For the adhesive layer 104, a glass material of low-melting-point glasscan also be used. In that case, paste containing glass powder (alsocalled a frit material) and a binder is applied to the first substrate101 or the second substrate 111, and the paste is subjected to heattreatment so that the binder is removed and the fused frit materialforms a glass layer. After that, the glass layer is melted by laserirradiation or the like and then solidified in a state where the glasslayer and the other substrate are in close contact with each other,whereby the first substrate 101 and the second substrate 111 can beattached to each other with the glass layer (also called a glass body).In the case of using an organic EL element as the display element, it isparticularly preferable to use such a glass material which does noteasily allow the passage of impurities such as moisture.

After the first substrate 101 and the second substrate 111 are attachedto each other, the first support substrate 102 and the second supportsubstrate 112 are each separated (FIG. 1D).

Here, the case where the second support substrate 112 is separated afterthe first support substrate 102 is separated will be described.

First, a surface of the second support substrate 112 on a side notprovided with the second substrate 111 is fixed to a suction stage orthe like. Next, a starting point of separation is formed between thefirst support substrate 102 and the first substrate 101. For example,the starting point of separation may be formed by inserting a sharpinstrument such as a knife into the boundary between the two substratesat an end portion of the first support substrate 102 or the firstsubstrate 101. Alternatively, the starting point of separation may beformed by dripping a liquid that has low surface tension (such asalcohol or water) onto the end portion so that the liquid penetratesinto the boundary between the two substrates.

Then, by applying physical force gradually from the starting point ofseparation in a direction substantially perpendicular to the attachmentsurfaces, separation can be easily caused without damage to the firstsupport substrate 102. At this time, for example, separation may becaused by attaching tape or the like to the first support substrate 102and pulling the tape in the aforementioned direction, or separation maybe caused by pulling an end portion of the first support substrate 102with a hook-like member. Alternatively, separation may be caused byattaching a member capable of vacuum suction to the back side of thefirst support substrate 102.

At the time of separation, static electricity might be generated and thefirst substrate 101 or the second substrate 111 might be chargedtherewith. When the first substrate 101 or the second substrate 111 ischarged, a circuit or an element in the element layer 103 or the sensorlayer 113 might be damaged by electrostatic discharge (ESD). In order tosuppress this, separation is preferably caused in a state where aconductive liquid (e.g., an ionic liquid, water including ions such ascarbonated water, or the like) is dripped onto the starting point ofseparation and the liquid is constantly in contact with the separationinterface between the first support substrate 102 and the firstsubstrate 101. Alternatively, separation may be caused while thegeneration of ESD is being suppressed using an ionizer or the like.

Next, the second support substrate 112 is separated. At this time, asurface of the first substrate 101 on a side not provided with theelement layer 103 is fixed to a suction stage or the like, and thesecond support substrate 112 and the second substrate 111 are separatedfrom each other by a method similar to those described above.

Note that here the second support substrate 112 is separated after thefirst support substrate 102 is separated, but there is no limitation onthe order. For example, the first support substrate 102 may be separatedafter the second support substrate 112 is separated.

Through the above steps, a display device 100 including a touch sensorand having a very small total thickness can be manufactured with highyield (FIG. 1E).

In the display device 100, the first substrate 101 and the secondsubstrate 111 are attached to each other with the adhesive layer 104,and the element layer 103 formed over the first substrate 101 andincluding the display element faces the sensor layer 113 formed over thesecond substrate 111 and including the sensor element. In addition, thefirst substrate 101 and the second substrate 111 are each characterizedby having a very small thickness of 10 μm to 200 μm.

The display device 100 can be formed with the two substrates, the secondsubstrate 111 provided with the touch sensor and the first substrate 101provided with the display element; thus, the total thickness of thedisplay device 100 can be reduced. In addition, the second substrate 111and the first substrate 101 can be attached to each other with highalignment accuracy because the two substrates are provided with therespective support substrates during the attachment.

The display device 100 can also have flexibility because of its verysmall total thickness. Accordingly, an electronic device having a curveddisplay portion, an electronic device whose display portion can becurved, or the like can be obtained.

The above is the description of this manufacturing method example.

[Manufacturing Method Example 2]

An example of a method for manufacturing a display device different fromthat in Manufacturing Method Example 1 will be described below.Specifically, a display device including color filters will bedescribed. Note that description of the portions already described inManufacturing Method Example 1 is omitted or is simplified.

First, as in Manufacturing Method Example 1, the element layer 103 isformed over the first substrate 101 which is fixed to the first supportsubstrate 102. In addition, the sensor layer 113 is formed over thesecond substrate 111 which is fixed to the second support substrate 112.

Then, a color filter layer 123 is formed over a third substrate 121which is fixed to a third support substrate 122 (FIG. 2A).

The third support substrate 122 can be similar to that of the firstsupport substrate 102, and the third substrate 121 can be similar tothat of the first substrate 101.

The color filter layer 123 includes a red color filter 124, a greencolor filter 125, and a blue color filter 126. The color filters arearranged so as to correspond to the respective pixels included in theelement layer 103. Further, a black matrix 127 may be provided betweenthe color filters. An overcoat may be provided so as to cover the colorfilters and the black matrix 127.

The color filters and the black matrix 127 may be formed usingappropriate materials and methods, and are preferably formed using aphotolithography method in the case where the pixel resolution is high.

It is preferable that the third substrate 121 be provided with a markerused for alignment at the time of later attachment to the firstsubstrate 101. The marker may be formed at the same time as the colorfilters and the black matrix 127, or may be formed separately.

Note that there is no limitation on the order of formation of theelement layer 103, the sensor layer 113, and the color filter layer 123,which may be formed separately.

Next, the stacked substrate of the first support substrate 102 and thefirst substrate 101 and the stacked substrate of the third supportsubstrate 122 and the third substrate 121 are arranged so that theelement layer 103 and the color filter layer 123 face each other, andthe first substrate 101 and the third substrate 121 are attached to eachother with the adhesive layer 104.

At this time, the first substrate 101 and the third substrate 121 can beattached while being fixed to the first support substrate 102 and thethird support substrate 122, respectively. Thus, the pixels included inthe element layer 103 and the color filters of the color filter layer123 can be aligned with high accuracy. Therefore, even when very thinsubstrates are used as the first substrate 101 and the third substrate121, a display device having a high pixel resolution can be obtained.

Next, the third support substrate 122 and the third substrate 121 areseparated from each other (FIG. 2B). The third support substrate 122 andthe third substrate 121 may be separated in a manner similar to that inManufacturing Method Example 1.

Next, the stacked substrate of the second support substrate 112 and thesecond substrate 111 provided with the sensor layer 113 is attached tothe back side of the third substrate 121 (a side opposite to the side onwhich the color filter layer 123 is provided) with an adhesive layer105. In that case, the attachment is performed so that the sensor layer113 faces the side of the first substrate 101 on which the element layer103 is formed.

The adhesive layer 105 can be similar to the adhesive layer 104.Alternatively, a double-sided adhesive sheet or the like can be used asthe adhesive layer 105. Note that in the case where the adhesive layer105 is provided so as to overlap with the pixels, a light-transmittingmaterial is used for the adhesive layer 105.

After that, the first substrate 101 and the first support substrate 102are separated from each other, and the second substrate 111 and thesecond support substrate 112 are separated from each other (FIG. 2C).These substrates may be separated in manners similar to those inManufacturing Method Example 1.

Through the above steps, a display device 110 including a touch sensorand a color filter and having a very small total thickness can bemanufactured (FIG. 2D).

In the display device 110, the first substrate 101 and the thirdsubstrate 121 are attached to each other with the adhesive layer 104,and the element layer 103 formed over the first substrate 101 andincluding a display element faces the color filter layer 123 formed overthe third substrate 121. In addition, the second substrate 111 providedwith the sensor layer 113 and the third substrate 121 are attached toeach other with the adhesive layer 105 so that a side of the thirdsubstrate 121 on which the color filter layer 123 is not provided facesthe sensor layer 113. Furthermore, the first substrate 101, the secondsubstrate 111, and the third substrate 121 are each characterized byhaving a very small thickness of 10 μm to 200 μm.

The display device 110 having such a structure includes the color filterlayer 123, and therefore can have high pixel color purity and candisplay high-quality images. The touch sensor is provided on the displaysurface side of the display device 110.

With the use of such a manufacturing method, a display device having avery small total thickness can be manufactured with high yield even whenhaving a structure in which three substrates provided with a touchsensor, a display element, and a color filter, respectively, arestacked. When the third substrate 121 provided with the color filterlayer 123 and the first substrate 101 provided with the display elementare attached to each other, the substrates are provided with therespective support substrates. Thus, misalignment of color filters andpixels can be suppressed, and the two substrates can be attached to eachother with high alignment accuracy. Thus, the display device 110 canhave a very high pixel resolution (e.g., 300 ppi or higher, preferably400 ppi or higher, and more preferably 500 ppi or higher) and have avery small total thickness.

The display device 110 can also have flexibility because of its verysmall total thickness. Accordingly, an electronic device having a curveddisplay portion, an electronic device whose display portion can becurved, or the like can be obtained.

The above is the description of this manufacturing method example.

Modified Example 1

A method for manufacturing a display device partly different from thatin Manufacturing Method Example 2 will be described below. Note thatdescription of the portions already described above is omitted or issimplified.

First, as in Manufacturing Method Example 2, the stacked substrate ofthe first support substrate 102 and the first substrate 101 and thestacked substrate of the third support substrate 122 and the thirdsubstrate 121 are arranged so that the element layer 103 and the colorfilter layer 123 face each other, and the first substrate 101 and thethird substrate 121 are attached to each other with the adhesive layer104.

Next, the first support substrate 102 and the first substrate 101 areseparated from each other (FIG. 3A). The first support substrate 102 maybe separated in a manner similar to that in Manufacturing Method Example1.

Next, the stacked substrate of the second support substrate 112 and thesecond substrate 111 provided with the sensor layer 113 is attached tothe back side of the first substrate 101 (a side opposite to the side onwhich the element layer 103 is not formed) with the adhesive layer 105.In that case, the attachment is performed so that the sensor layer 113faces the side of the third substrate 121 on which the color filterlayer 123 is formed.

For the adhesive layer 105, the material given as an example inManufacturing Method Example 2 can be used. Since the sensor layer 113is provided on a side opposite to the display surface side, a materialused for the adhesive layer 105 does not necessarily need to have alight-transmitting property even when the adhesive layer 105 is providedso as to overlap with pixels.

After that, the second support substrate 112 and the second substrate111 are separated from each other, and the third support substrate 122and the third substrate 121 are separated from each other (FIG. 3B).These substrates may be separated in manners similar to those inManufacturing Method Example 1.

Through the above steps, a display device 120 provided with a touchsensor on a side opposite to the display surface side and having a verysmall total thickness can be manufactured (FIG. 3C).

In the display device 120, the first substrate 101 and the thirdsubstrate 121 are attached to each other with the adhesive layer 104,and the element layer 103 formed over the first substrate 101 andincluding a display element faces the color filter layer 123 formed overthe third substrate 121. In addition, the second substrate 111 providedwith the sensor layer 113 and the first substrate 101 are attached toeach other with the adhesive layer 105 so that a side of the firstsubstrate 101 on which the element layer 103 is not provided faces thesensor layer 113. Furthermore, the first substrate 101, the secondsubstrate 111, and the third substrate 121 are each characterized byhaving a very small thickness of 10 μm to 200 μm.

The display device 120 having such a structure includes the color filterlayer 123, and therefore can have high pixel color purity and candisplay high-quality images. The touch sensor is provided on the sideopposite to the display surface side of the display device 120. Sincethe touch sensor is provided on the side opposite to the display surfaceside, an input operation can be performed without display obscured by auser's finger or the like, which is suitable for an electronic devicecapable of running game content involving a touch input based on adisplayed image or playing video content such as a movie.

The display device 120 can also have flexibility because of its verysmall total thickness. Accordingly, an electronic device having a curveddisplay portion, an electronic device whose display portion can becurved, or the like can be obtained.

The above is the description of this modified example.

[Manufacturing Method Example 3]

In this manufacturing method example, an example of a method formanufacturing a display device which is different from the abovemanufacturing method examples will be described below.

First, as in Manufacturing Method Example 1, the element layer 103 isformed over the first substrate 101 which is fixed to the first supportsubstrate 102.

Then, a stack of the sensor layer 113 and the color filter layer 123 isformed over the second substrate 111 which is fixed to the secondsupport substrate 112 (FIG. 4A).

First, as in Manufacturing Method Example 1, the sensor layer 113 isformed over the second substrate 111 which is fixed to the secondsupport substrate 112.

Next, an insulating layer 128 is formed over the sensor layer 113 so asto cover the second sensor electrode 115.

The insulating layer 128 can be formed by a variety of formation methodsusing a light-transmitting organic or inorganic insulating material. Itis preferable to use an organic resin for the insulating layer 128, inwhich case the insulating layer 128 can effectively cover steps due tothe first sensor electrode 114 and the second sensor electrode 115 ofthe sensor layer 113 and can have a relatively flat surface, whereby theunevenness of the thickness of color filters which are formed later canbe suppressed and the display quality of the display device can beimproved.

Then, the color filter layer 123 is formed over the insulating layer128. The color filter layer 123 can be formed in a manner similar tothat in Manufacturing Method Example 2.

Next, the stacked substrate of the first support substrate 102 and thefirst substrate 101 and the stacked substrate of the second supportsubstrate 112 and the second substrate 111 are arranged so that theelement layer 103 and the color filter layer 123 face each other, andthe first substrate 101 and the second substrate 111 are attached toeach other with the adhesive layer 104 (FIG. 4B).

At this time, the first substrate 101 and the second substrate 111 canbe attached while being fixed to the first support substrate 102 and thesecond support substrate 112, respectively. Thus, the pixels included inthe element layer 103 and the color filters of the color filter layer123 can be aligned with high accuracy. Therefore, even when very thinsubstrates are used as the first substrate 101 and the second substrate111, a display device having a high pixel resolution can be obtained.

After that, the first substrate 101 and the first support substrate 102are separated from each other, and the second substrate 111 and thesecond support substrate 112 are separated from each other (FIG. 4C).These substrates may be separated in manners similar to those inManufacturing Method Example 1.

Through the above steps, a display device 130 including a touch sensorand a color filter and having a very small total thickness can bemanufactured (FIG. 4D).

In the display device 130, the first substrate 101 and the secondsubstrate 111 are attached to each other with the adhesive layer 104,and the element layer 103 formed over the first substrate 101 andincluding a display element faces the stack of the sensor layer 113 andthe color filter layer 123 formed over the second substrate 111.Furthermore, the first substrate 101 and the second substrate 111 areeach characterized by having a very small thickness of 10 μm to 200 μm.

In the display device 130 having such a structure, the sensor layer 113and the color filter layer 123 are stacked over one substrate; thus, thedisplay device 130 can be formed with two substrates. Accordingly, thedisplay device 130 can have a smaller total thickness. The color filterscan be directly formed over the touch sensors, and the two substratesare attached to each other while being fixed to the respective supportsubstrates. Therefore, the touch sensors and the color filters, thetouch sensors and the pixels, and the color filters and the pixels canbe aligned to each other with high accuracy; thus, a display devicehaving a very high pixel resolution and including highly accurate touchsensors can be obtained.

The display device 130 can also have flexibility because of its verysmall total thickness. Accordingly, an electronic device having a curveddisplay portion, an electronic device whose display portion can becurved, or the like can be obtained.

The above is the description of this manufacturing method example.

The display devices given as examples in this embodiment each include atouch sensor and have a sufficiently small total thickness. By themethods for manufacturing the display devices given as examples in thisembodiment, the display devices having a sufficiently small totalthickness can be manufactured with high mass productivity and highyield.

In the methods for manufacturing the display devices given as examplesin this embodiment, the steps of forming the element layer, the sensorlayer, and the color filter layer over the stacked substrates are alsodescribed. Alternatively, a stacked substrate provided with an elementlayer, a sensor layer, or a color filter layer in advance may be used.Thus, for example, manufacturing a display device using a stackedsubstrate provided with an element layer in advance and a stackedsubstrate provided with a sensor layer in advance is also one embodimentof the present invention. In addition, manufacturing a display deviceusing a stacked substrate provided with a color filter layer in advanceand a stacked substrate provided with a stack of a sensor layer and acolor filter layer in advance is also one embodiment of the presentinvention.

This embodiment can be implemented in an appropriate combination withany of the other embodiments described in this specification.

Embodiment 2

In this embodiment, a more specific configuration example of a displaydevice which can be manufactured by any of the methods for manufacturingthe display devices given as examples in Embodiment 1 will be described.Note that description of the portions already described in Embodiment 1is omitted or is simplified.

Configuration Example

FIG. 5A is a schematic perspective view of a display device 200described in this configuration example. Note that FIGS. 5A and 5Billustrate only major components for simplicity.

The display device 200 includes a display portion 201 and a touch sensor202 between a first substrate 101 and a second substrate 111. Inaddition, an FPC 204 is attached to the first substrate 101.

FIG. 5B is a schematic diagram in which the first substrate 101 and thesecond substrate 111 in FIG. 5A are spaced apart.

The first substrate 101 is provided with the display portion 201, aplurality of wirings 206 electrically connected to the display portion201, and a plurality of wirings 207 electrically connected to the touchsensor 202 through contact portions 203. The plurality of wirings 206and the plurality of wirings 207 are led to the periphery of the firstsubstrate 101, and in the periphery, portions of these wirings form partof external connection electrodes 205 for electrical connection to theFPC 204.

The display portion 201 includes a pixel portion 211 including aplurality of pixels, a source driver circuit 212, and a gate drivercircuit 213. Although FIG. 5B illustrates a configuration in which twosource driver circuits 212 are positioned on both sides of the pixelportion 211, one source driver circuit 212 may be positioned along oneside of the pixel portion 211.

As a display element which can be used in the pixel portion 211 of thedisplay portion 201, any of a variety of display elements such as anorganic EL element, a liquid crystal element, and a display elementperforming display by an electrophoretic method or the like can be used.

The second substrate 111 is provided with the touch sensor 202. Thetouch sensor 202 is provided over a surface of the second substrate 111on a side facing the first substrate 101. Note that in FIG. 5B,electrodes of the touch sensor 202 which are provided on the back sideof the second substrate 111 (the back side of the diagram) are indicatedby solid lines for clarity.

The touch sensor 202 illustrated in FIG. 5B is an example of a projectedcapacitive touch sensor. The touch sensor 202 includes a first sensorelectrode 114 and a second sensor electrode 115.

The first sensor electrode 114 and the second sensor electrode 115 areelectrically connected to the wirings 207 provided over the firstsubstrate 101 through the contact portions 203. Thus, the touch sensor202 provided over the second substrate 111 can be driven through the FPC204 attached to the first substrate 101. Note that a specificconfiguration example of the contact portions 203 will be describedlater.

Here, the first sensor electrode 114 and the second sensor electrode 115are each in the form of a series of quadrangles arranged in onedirection as illustrated in FIGS. 5A and 5B. The electrodes arepreferably arranged so that the area of crossing portions of the firstsensor electrode 114 and the second sensor electrode 115 becomes assmall as possible. Such a shape can reduce the area of regions where theelectrodes are not provided and decrease luminance unevenness of lightpassing through the first substrate 111 which may be caused by adifference in transmittance depending on whether the electrodes areprovided or not.

Note that the shapes of the first sensor electrode 114 and the secondsensor electrode 115 are not limited thereto and can be any of a varietyof shapes. For example, a plurality of first sensor electrodes 114 maybe arranged so as to have as small a gap as possible, and a plurality ofsecond sensor electrodes 115 thereover may be provided so as to bespaced apart and have regions not overlapping with the first sensorelectrodes 114. In that case, between two adjacent second sensorelectrodes 115, it is preferable to provide a dummy electrode which iselectrically insulated from these electrodes, whereby the area ofregions having different transmittances can be reduced.

When external connection electrodes connected to the FPC 204 or the likefor exchanging signals with the touch sensor 202 are provided asdescribed above on the side of the first substrate 101 where the displayportion 201 is formed, external connection electrodes for both the touchsensor and the display portion 201 can be provided on one surface sideof the display device 200. Thus, the area necessary for connection ofthe FPC 204 can be reduced. Furthermore, when the layout of wirings isdevised as illustrated in FIGS. 5A and 5B, only one FPC 204 needs to beprovided. When the display device 200 is applied to an electronicdevice, the area occupied by the display device 200 in the electronicdevice can be reduced and the electronic device can therefore bedesigned more freely.

[Cross-Sectional Configuration Example 1]

A cross-sectional configuration example of the display device 200 inwhich an organic EL element is included in the display portion 201 willbe described below.

FIG. 6 is a schematic cross-sectional view of a region including the FPC204 and the gate driver circuit 213 along the section line A-B, a regionincluding the pixel portion 211 along the section line C-D, and a regionincluding the contact portion 203 along the section line E-F, in thedisplay device 200 illustrated in FIG. 5A.

Peripheral portions of the first substrate 101 and the second substrate111 are attached to each other with the adhesive layer 104. In a regionsurrounded by the first substrate 101, the second substrate 111, and theadhesive layer 104, at least the pixel portion 211 is provided.

In FIG. 6, the gate driver circuit 213 includes a circuit in whichn-channel transistors, transistors 231 and 232, are used in combination,as an example. Note that the gate driver circuit 213 is not limited tothis structure and may include various CMOS circuits in which ann-channel transistor and a p-channel transistor are used in combinationor a circuit in which p-channel transistors are used in combination.Note that the same applies to the source driver circuit 212. Although adriver-integrated structure in which the gate driver circuit 213 and thesource driver circuit 212 are formed over an insulating surface providedwith the display portion 201 is described in this configuration example,the gate driver circuit 213 or the source driver circuit 212, or bothmay be formed over a surface different from the insulating surfaceprovided with the display portion 201. For example, a driver circuit ICmay be mounted by a COG method, or a flexible substrate (FPC) mountedwith a driver circuit IC by a COF method may be mounted.

FIG. 6 shows a cross-sectional structure of one pixel as an example ofthe pixel portion 211. The pixel includes a switching transistor 233, acurrent control transistor 234, and a first electrode layer 221 that iselectrically connected to an electrode (a source electrode or a drainelectrode) of the transistor 234. An insulating layer 235 is provided soas to cover an end portion of the first electrode layer 221, and aspacer 236 is provided over the insulating layer 235 in a regionoverlapping with a black matrix 242 which is described later. When aplurality of spacers 236 is provided in the pixel portion 211, the firstsubstrate 101 and the second substrate 111 can be prevented from gettingunnecessarily close to each other, and the display device can have highreliability.

The spacer 236 is preferably formed using an organic resin materialbecause it can be formed thick. For example, the spacer 236 can beformed using a positive or negative photosensitive resin. When alight-blocking material is used for the spacer 236, the spacer 236blocks light emitted from a light-emitting element 220 in an adjacentpixel, thereby preventing color mixture between the adjacent pixels.

Note that there is no particular limitation on the structures of thetransistors included in the pixel portion 211, the source driver circuit212, and the gate driver circuit 213. For example, a forward staggeredtransistor or an inverted staggered transistor may be used. Further, atop-gate transistor or a bottom-gate transistor may be used. As asemiconductor material used for the transistors, for example, asemiconductor material such as silicon or germanium or an oxidesemiconductor containing at least one of indium, gallium, and zinc maybe used.

Further, there is no particular limitation on the crystallinity of asemiconductor used for the transistors, and an amorphous semiconductoror a semiconductor having crystallinity (a microcrystallinesemiconductor, a polycrystalline semiconductor, a single crystalsemiconductor, or a semiconductor partly including crystal regions) maybe used. A semiconductor having crystallinity is preferably used, inwhich case deterioration of transistor characteristics can be reduced.

Typical examples of the oxide semiconductor containing at least one ofindium, gallium, and zinc include an In—Ga—Zn—O-based metal oxide. Anoxide semiconductor having a wider band gap and a lower carrier densitythan silicon is preferably used because off-state leakage current can bereduced. Details of preferred oxide semiconductors will be describedbelow in another embodiment.

The light-emitting element 220 includes the first electrode layer 221, asecond electrode layer 223, and an EL layer 222 provided therebetween.The light-emitting element 220 will be described below.

In the light-emitting element 220, a light-transmitting material thattransmits light emitted from the EL layer 222 is used for an electrodelayer provided on the light exit side.

As the light-transmitting material, a conductive oxide such as indiumoxide, indium tin oxide, indium zinc oxide, zinc oxide, or zinc oxide towhich gallium is added can be used. Alternatively, graphene may be used.Other examples include a metal material such as gold, silver, platinum,magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper,palladium, or titanium and an alloy material containing any of thesemetal materials. Alternatively, a nitride of the metal material (e.g.,titanium nitride) or the like may be used. In the case of using themetal material or the alloy material (or the nitride thereof), thethickness is set small enough to be able to transmit light.Alternatively, a stack of films of any of the above materials can beused as a conductive layer. For example, a stack of films of asilver-magnesium alloy and indium tin oxide is preferably used becauseconductivity can be increased.

Such an electrode layer is formed by an evaporation method, a sputteringmethod, or the like. Alternatively, a discharging method such as anink-jet method, a printing method such as a screen printing method, or aplating method may be used.

Note that when a film of the above light-transmitting conductive oxideis formed by a sputtering method, the use of a deposition atmospherecontaining argon and oxygen allows the conductive oxide to be capable oftransmitting more light.

Further, in the case where a film of the conductive oxide is formed overthe EL layer 222, it is preferable to stack a first conductive oxidefilm formed under an atmosphere containing argon with reduced oxygenconcentration and a second conductive oxide film formed under anatmosphere containing argon and oxygen, in which case damage to the ELlayer 222 due to film formation can be reduced. In this case, in theformation of the first conductive oxide film, it is preferable to use anargon gas with high purity, for example, an argon gas whose dew point islower than or equal to −70° C., more preferably lower than or equal to−100° C.

For an electrode layer provided on a side opposite to the light exitside, a reflective material which reflects the light emission is used.

As a light reflective material, a metal material such as aluminum, gold,platinum, silver, nickel, tungsten, chromium, molybdenum, iron, cobalt,copper, or palladium or an alloy material containing any of these metalmaterials can be used. Alternatively, lanthanum, neodymium, germanium,or the like may be added to such a metal material or alloy material.Examples of alloy materials include alloys containing aluminum (aluminumalloys) such as an alloy of aluminum and titanium, an alloy of aluminumand nickel, and an alloy of aluminum and neodymium, alloys containingsilver such as an alloy of silver and copper, an alloy of silver,palladium, and copper, and an alloy of silver and magnesium, and thelike. An alloy of silver and copper is preferable because of its highheat resistance. Further, by stacking a metal film or a metal oxide filmin contact with a film containing aluminum, oxidation of the filmcontaining aluminum can be suppressed. Examples of the metal material orthe metal oxide material in contact with the film containing aluminuminclude titanium, titanium oxide, and the like. Alternatively, a stackof a film containing any of the above light-transmitting materials and afilm containing any of the above metal materials may be used. Forexample, a layered film of silver and indium tin oxide, a layered filmof a silver-magnesium alloy and indium tin oxide, or the like can beused.

Such an electrode layer is fainted by an evaporation method, asputtering method, or the like. Alternatively, a discharging method suchas an ink-jet method, a printing method such as a screen printingmethod, or a plating method may be used.

The EL layer 222 includes at least a layer containing a light-emittingorganic compound (hereinafter also referred to as a light-emittinglayer), and may be either a single layer or a stack of plural layers.One example of the structure in which a plurality of layers is stackedis a structure in which a hole-injection layer, a hole-transport layer,a light-emitting layer, an electron-transport layer, and anelectron-injection layer are stacked in this order from an anode side.Note that not all of these layers except the light-emitting layer arenecessarily provided in the EL layer 222. Further, each of these layersmay be provided in duplicate or more. Specifically, in the EL layer 222,a plurality of light-emitting layers may be stacked, or anotherhole-injection layer may be stacked over the electron-injection layer.Furthermore, another component such as an electron-relay layer may beprovided as appropriate as an intermediate layer, in addition to acharge-generation layer. Alternatively, a plurality of light-emittinglayers exhibiting different colors may be stacked. For example, a whiteemission can be obtained by stacking two or more light-emitting layersof complementary colors.

The EL layer 222 can be formed by a vacuum evaporation method, adischarging method such as an ink-jet method or a dispensing method, acoating method such as a spin-coating method, a printing method, or thelike.

In this embodiment, a reflective material is used for the firstelectrode layer 221, and a light-transmitting material is used for thesecond electrode layer 223. Thus, the light-emitting element 220 is atop-emission light-emitting element, and emits light to the secondsubstrate 111 side.

The above is the description of the light-emitting element 220.

The first substrate 101 is provided with an insulating layer 237 incontact with an upper surface of the first substrate 101, an insulatinglayer 238 functioning as a gate insulating layer of transistors, andinsulating layers 239 and 241 covering the transistors.

The insulating layer 237 is provided in order to prevent diffusion ofimpurities included in the first substrate 101. The insulating layers238 and 239, which are in contact with semiconductor layers of thetransistors, are preferably formed using a material which preventsdiffusion of impurities that promote degradation of the transistors. Forthese insulating layers, for example, an oxide, a nitride, or anoxynitride of a semiconductor such as silicon or a metal such asaluminum can be used. Alternatively, a stack of such inorganicinsulating materials or a stack of such an inorganic insulating materialand an organic insulating material may be used. Note that the insulatinglayers 237 and 239 are not necessarily provided when not needed.

The insulating layer 241 functions as a planarization layer which coverssteps due to the transistors, a wiring, or the like provided therebelow.For the insulating layer 241, it is preferable to use an organic resinmaterial such as polyimide or acrylic. An inorganic insulating materialmay be used as long as high planarity can be obtained.

Here, a layer including the transistors and the light-emitting element220 corresponds to the element layer 103. In this configuration example,a stack of components from an upper surface of the insulating layer 237to the second electrode layer 223 corresponds to the element layer 103.

The second substrate 111 is provided with the first sensor electrode114, the insulating layer 116, and the second sensor electrode 115 on aside facing the light-emitting element 220, and a stack of these layerscorresponds to the sensor layer 113 in Embodiment 1.

A light-transmitting material which transmits light emitted from thelight-emitting element 220 is used for the first sensor electrode 114and the second sensor electrode 115. For example, any of theabove-described light-transmitting conductive materials which can beused in the light-emitting element 220 can be used.

The insulating layer 116 insulates the first sensor electrode 114 andthe second sensor electrode 115 from each other. A light-transmittingmaterial which transmits light emitted from the light-emitting element220 is used for the insulating layer 116. For example, an inorganicinsulating material, an organic insulating material, or a stack of thesematerials can be used.

As illustrated in FIGS. 5A and 5B and FIG. 6, the first sensor electrode114 and the second sensor electrode 115 may be provided not only in aregion overlapping with the pixel portion 211 but also in a regionoverlapping with the source driver circuit 212 or the gate drivercircuit 213.

An insulating layer 128 is provided so as to cover the first sensorelectrode 114 and the second sensor electrode 115 at least in the regionoverlapping with the pixel portion 211. In addition, the insulatinglayer 128 is provided with the black matrix 242 and a color filter 243on a side facing the light-emitting element 220.

The insulating layer 128 protects the second sensor electrode 115 andcan insulate adjacent second sensor electrodes 115 from each other byfilling a gap therebetween. For the insulating layer 128, it ispreferable to use a material which provides high coverage in order toeffectively cover a step due to the first sensor electrode 114 or thesecond sensor electrode 115. For example, a material similar to that ofthe insulating layer 241 is used. When the insulating layer 128 has aflat surface, the color filter 243 can have a uniform thickness, whichenables the display device to have higher display quality.

The color filter 243 is provided in order to adjust the color of lightemitted from the light-emitting element 220 to increase the colorpurity. For example, in a full-color display device using whitelight-emitting elements, a plurality of pixels provided with colorfilters of different colors is used. In that case, the color filters maybe those of three colors of R (red), G (green), and B (blue) or fourcolors (yellow (Y) in addition to these three colors). Further, a white(W) pixel may be added to R, and B pixels (and a Y pixel). That is,color filters of four colors (or five colors) may be used.

Further, the black matrix 242 is provided between adjacent color filters243. The black matrix 242 blocks light emitted from the light-emittingelement 220 in an adjacent pixel, thereby preventing color mixturebetween the adjacent pixels. In one configuration, the black matrix 242may be provided only between adjacent pixels of different emissioncolors and not between pixels of the same emission color. When the colorfilter 243 is provided so that its end portion overlaps with the blackmatrix 242, light leakage can be reduced. The black matrix 242 can beformed using a material that blocks light emitted from thelight-emitting element 220, for example, a metal material, an organicresin material including a pigment, or the like. Note that it ispreferable to provide the black matrix 242 also in a region overlappingwith the gate driver circuit 213 or the like besides the pixel portion211 as illustrated in FIG. 6, in which case undesired leakage of guidedlight or the like can be prevented.

In addition, an overcoat may be provided so as to cover the color filter243 and the black matrix 242. The overcoat protects the color filter 243and the black matrix 242 and suppresses the diffusion of impuritiesincluded in the color filter 243 and the black matrix 242. For theovercoat, a material which transmits light emitted from thelight-emitting element 220 is used, and an inorganic insulating materialor an organic insulating material can be used.

The first substrate 101 and the second substrate 111 are attached toeach other with the adhesive layer 104. In this configuration example, aglass material is used for the first substrate 101 and the secondsubstrate 111, and a glass material of low-melting-point glass is usedfor the adhesive layer 104. With the use of such materials, the entry ofimpurities, which may cause degradation of the light-emitting element220 or the transistors, from the adhesive layer 104 can be effectivelysuppressed, which enables the display device to have extremely highreliability.

In particular, in the case where an oxide semiconductor is used as asemiconductor for the transistors, impurities such as hydrogen containedin an oxide semiconductor film as described below in another embodimentcause the threshold voltage of the transistors to be shifted in thenegative direction, for example. Therefore, it is quite effective toseal a region provided with the transistors with the first substrate101, the second substrate 111, and the adhesive layer 104 which areformed with a glass material, thereby suppressing the entry of impurityelements including hydrogen.

In the contact portion 203, the wiring 207 and an electrode 244 which iselectrically connected to the wiring 207 are provided over the firstsubstrate 101. The wiring 207 is formed by processing the sameconductive film as the source electrode and the drain electrode of thetransistor. The electrode 244 is formed by processing the sameconductive film as the first electrode layer 221, and is electricallyconnected to the wiring 207 through an opening provided in theinsulating layer 239 and the insulating layer 241. The wiring 207 andthe electrode 244 provided in the contact portion 203 are preferablyformed in the above manner by processing the conductive films used toform the transistors and the light-emitting element 220 because thecontact portion 203 can be easily formed without increasing steps.

On the second substrate 111 side, the second sensor electrode 115 isprovided so as to extend to the contact portion 203 and so as to have anexposed surface in the contact portion 203. Although not illustrated,the same applies to a contact portion for the first sensor electrode114.

Furthermore, a resin layer 246 in which conductive particles 245 aredispersed is provided in the contact portion 203. By the contact of theconductive particles 245 in the resin layer 246 with both the secondsensor electrode 115 and the electrode 244, the second sensor electrode115 and the wiring 207 are electrically connected to each other.

As the conductive particles 245, particles of an organic resin, silica,or the like coated with a metal material are used. It is preferable touse nickel or gold as the metal material because contact resistance canbe decreased. It is also preferable to use particles each coated withlayers of two or more kinds of metal materials, such as particles coatedwith nickel and further with gold.

As a material of the resin layer 246 in which the conductive particles245 can be dispersed, it is preferable to use a curable organic resinsuch as a heat curable organic resin or a photocurable organic resin.

It is preferable that the conductive particles 245 provided between thesecond sensor electrode 115 and the electrode 244 be deformed by beingcrushed under vertical pressure. By such deformation, the contact areabetween the conductive particles 245 and the second sensor electrode 115or the electrode 244 is increased, whereby electrical connection can besecured. Note that, for convenience, the conductive particles 245 areillustrated in the schematic cross-sectional view in FIG. 6 as having anelliptical cross-sectional shape with a long axis in a directionperpendicular to the substrates. However, in many actual cases, theconductive particles 245 have a circular cross-sectional shape or anelliptical cross-sectional shape with a long axis component in adirection parallel to the substrates.

In the configuration illustrated in FIG. 6, the adhesive layer 104 isprovided so as to surround at least the pixel portion 211 including thelight-emitting element 220, and the contact portion 203 is providedoutside the adhesive layer 104. In the case where a glass material isused for the adhesive layer 104, it is particularly preferable toprovide the contact portion 203 outside the adhesive layer 104 asdescribed above because it is possible to suppress diffusion ofimpurities such as water, which are contained in an organic resin or thelike used in the contact portion 203, into a region inside the adhesivelayer 104.

Further, as the layers which are provided so as to extend both in theregion sealed with the adhesive layer 104 and in the region outside thesealed region as illustrated in FIG. 6, it is preferable not to uselayers of a material such as an organic material which allows thepassage of water or hydrogen. This makes it possible to effectivelysuppress the entry of water or hydrogen from the outside and to obtain adisplay device having high reliability.

Note that when a curable resin is used for the adhesive layer 104, theadhesive layer 104 may serve also as the resin layer 246. In that case,the adhesive layer 104 may be provided also in the contact portion 203,and the conductive particles 245 may be dispersed in part of theadhesive layer 104 in the contact portion 203. This eliminates thenecessity of locating the contact portion 203 outside the adhesive layer104 and therefore enables the display device to have a narrower frame.Note that it is preferable in that case to disperse a drying agent inthe adhesive layer 104. For example, a substance which adsorbs moistureby chemical adsorption, such as an oxide of an alkaline earth metal(e.g., calcium oxide or barium oxide), can be used. Alternatively, asubstance which adsorbs moisture by physical adsorption, such as zeoliteor silica gel, may be used as the drying agent.

The wiring 206 is provided so as to extend to the outside of the regionsealed with the adhesive layer 104 and is electrically connected to thegate driver circuit 213 (or the source driver circuit 212). Part of anend portion of the wiring 206 forms part of the external connectionelectrode 205. In this configuration example, the external connectionelectrode 205 is formed by a stack of a conductive film used for thesource electrode and the drain electrode of the transistor and aconductive film used for the gate electrode of the transistor. Theexternal connection electrode 205 is preferably formed by a stack of aplurality of conductive films as described above because mechanicalstrength against a pressure bonding step performed on the FPC 204 or thelike can be increased.

A connection layer 208 is provided in contact with the externalconnection electrode 205. The FPC 204 is electrically connected to theexternal connection electrode 205 through the connection layer 208. Forthe connection layer 208, an anisotropic conductive film (ACF),anisotropic conductive paste (ACP), or the like can be used.

Although not illustrated here, the wiring 207 is provided so as toextend to an end portion of the first substrate 101, and part of an endportion of the wiring 207 forms part of the external connectionelectrode 205 and is electrically connected to the FPC 204.

The end portions of the wiring 206, the wiring 207, and the externalconnection electrode 205 are preferably covered with an insulating layerso that surfaces thereof are not exposed because oxidation of thesurfaces and defects such as short-circuit can be suppressed. In thatcase, the insulating layer covering the wiring 206, the wiring 207, andthe external connection electrode 205 are preferably formed byprocessing the same film as any of the insulating layers included in thepixel portion 211 because the insulating layer can be formed withoutincreasing steps.

In FIG. 6, a reinforcing material 209 is provided between the FPC 204and the adhesive layer 104 so as to be in contact with both the FPC 204and the second substrate 111. In this configuration example, anextremely thin glass substrate is used as the first substrate 101; thus,a region between the FPC 204 and the adhesive layer 104 has a relativelylow mechanical strength. Therefore, a crack might be caused in thatregion by mechanical force applied to the vicinity of the FPC 204 whenthe display device is incorporated into an electronic device, forexample. The reinforcing material 209 provided as described above canincrease the mechanical strength of the region between the FPC 204 andthe adhesive layer 104, which enables the display device to have highreliability.

As the reinforcing material 209, an organic resin material is preferablyused. For example, a curable organic resin such as a heat curableorganic resin, a photocurable organic resin, or a two-component typecurable organic resin can be used.

Note that the reinforcing material 209 may be provided also on the backside of the first substrate 101. When both sides of the first substrate101 are reinforced by the reinforcing material 209, the mechanicalstrength can be further increased, and damage to an extremely thindisplay device can be reduced.

The above is the description of this cross-sectional configurationexample. Such a configuration makes it possible to obtain a displaydevice which is extremely thin and has high mechanical strength and highreliability.

[Cross-sectional Configuration Example 2]

A cross-sectional configuration example of the display device 200 inwhich a liquid crystal element is included in the display portion 201will be described below. Note that description of the portions alreadydescribed above is omitted or is simplified.

FIG. 7 is a schematic cross-sectional view of the display devicedescribed in this configuration example. The display device in FIG. 7differs from the configuration described above in Cross-sectionalConfiguration Example 1, mainly in the pixel portion 211 and theadhesive layer 104.

The pixel portion 211 includes a liquid crystal element 250 usingin-plane switching (IPS) mode. In the liquid crystal element 250, theorientation of a liquid crystal is controlled by an electric fieldgenerated in a direction parallel to the substrate surface.

The pixel portion 211 includes at least one switching transistor 256 anda storage capacitor which is not illustrated. In addition, a firstelectrode layer 251 having a comb shape is provided over the insulatinglayer 241 so as to be electrically connected to a source electrode or adrain electrode of the transistor 256. Furthermore, a second electrodelayer 253 having a comb shape is provided so as to be insulated from thefirst electrode layer 251 on the same plane.

For at least one of the first and second electrode layers 251 and 253,any of the above-described light-transmitting conductive materials isused. It is preferable to use a light-transmitting conductive materialfor both of these electrode layers because the aperture ratio of thepixel can be increased.

Although the first electrode layer 251 and the second electrode layer253 are distinguished from each other in FIG. 7 by using different hatchpatterns, these electrode layers are preferably formed by processing thesame conductive film.

In the pixel portion 211, the second substrate 111 is provided with thecolor filter 243 and the black matrix 242 as in Cross-sectionalConfiguration Example 1. In FIG. 7, an overcoat 255 is provided so as tocover the color filter 243 and the black matrix 242. The overcoat 255can suppress diffusion of impurities such as a pigment, which areincluded in the color filter 243 and the black matrix 242, into a liquidcrystal 252.

In addition, a spacer 254 is provided in a region where the overcoat 255overlaps with the black matrix 242. The spacer 254 can be formed using amaterial similar to that of the spacer 236 in Cross-sectionalConfiguration Example 1. Although the spacer 254 is provided on thesecond substrate 111 side in this configuration example, the spacer 254may be provided on the first substrate 101 side.

The liquid crystal 252 is sealed at least in a region where the firstelectrode layer 251 and the second electrode layer 253 are provided.Here, the first electrode layer 251, the second electrode layer 253, andthe liquid crystal 252 form the liquid crystal element 250.

An image can be displayed in the following way: an electric field isgenerated in the horizontal direction by application of voltage betweenthe first electrode layer 251 and the second electrode layer 253,orientation of the liquid crystal 252 is controlled by the electricfield, and polarization of light from a backlight provided outside thedisplay device is controlled in each pixel.

An alignment film that controls orientation of the liquid crystal 252may be provided on a surface in contact with the liquid crystal 252. Alight-transmitting material is used for the alignment film. Although notillustrated here, polarizing plates are provided on outer sides of thefirst substrate 101 and the second substrate 111 with respect to theliquid crystal element 250. Moreover, a light guide plate may be used sothat light from the backlight enters through a side surface of thedisplay device.

In this configuration example, a color filter is provided in a regionoverlapping with the liquid crystal element 250; thus, a full-colorimage can be displayed using a backlight that emits white light. Withthe use of a plurality of light-emitting diodes (LEDs) which emit lightof different colors as a backlight, a time-division display method (afield-sequential driving method) can be employed. In the case ofemploying a time-division display method, the aperture ratio of eachpixel or the number of pixels per unit area can be increased becauseneither color filters nor subpixels from which light of red (R), green(G), or blue (B), for example, is obtained are needed.

As the liquid crystal 252, a thermotropic liquid crystal, a lowmolecular weight liquid crystal, a polymer liquid crystal, aferroelectric liquid crystal, an anti-ferroelectric liquid crystal, orthe like can be used. Moreover, a liquid crystal exhibiting a blue phaseis preferably used because an alignment film is not necessary and theviewing angle is wide.

Although the liquid crystal element 250 using IPS mode is described inthis configuration example, the mode of the liquid crystal element isnot limited to this example, and a twisted nematic (TN) mode, a fringefield switching (FFS) mode, an axially symmetric aligned micro-cell(ASM) mode, an optically compensated birefringence (OCB) mode, aferroelectric liquid crystal (FLC) mode, an anti-ferroelectric liquidcrystal (AFLC) mode, or the like can be used.

Here, the light-emitting element 250 preferably uses the IPS mode or theFFS mode. A liquid crystal element using such a mode does not require anelectrode to be provided on the second substrate 111 side. Thus, it ispossible to reduce the influence of parasitic capacitance generatedbetween an electrode of the touch sensor provided on the secondsubstrate 111 side and the electrode of the liquid crystal element,thereby improving the sensitivity of the touch sensor.

In this configuration example, the adhesive layer 104 serves also as theresin layer 246 used in the contact portion 203, as described as oneexample in Cross-sectional Configuration Example 1. For the adhesivelayer 104, a curable organic resin is used, and the adhesive layer 104is provided so as to overlap with the contact portion 203. In addition,the conductive particles 245 are dispersed in the region overlappingwith the contact portion 203. This enables the display device to have anarrow frame.

As illustrated in FIG. 7, layers formed using an organic material, suchas the insulating layer 241 and the insulating layer 128, are preferablyprocessed into island shapes so that these layers do not continuouslyextend both in the region provided with the pixel portion 211 and thegate driver circuit 213 (and the source driver circuit 212) and in theregion provided with the adhesive layer 104 and so that these layershave end portions between these regions. This makes it possible tosuppress diffusion of impurities such as moisture into the liquidcrystal element 250 or the transistor through the insulating layer 241,the insulating layer 128, or the like even when an organic resin is usedfor the adhesive layer 104.

The above is the description of this configuration example. Such aconfiguration makes it possible to obtain a display device which isextremely thin and has high mechanical strength and high reliability.

This embodiment can be implemented in an appropriate combination withany of the other embodiments described in this specification.

Embodiment 3

In this embodiment, a configuration example of a light-emitting elementwhich can be applied to a light-emitting device in one embodiment of thepresent invention will be described with reference to drawings.

The light-emitting element shown as an example in this embodimentincludes a first electrode layer, a second electrode layer, and a layercontaining a light-emitting organic compound (hereinafter referred to asan EL layer) between the first electrode layer and the second electrodelayer. One of the first and second electrode layers functions as ananode, and the other functions as a cathode. The EL layer is providedbetween the first electrode layer and the second electrode layer, and astructure of the EL layer may be appropriately determined in accordancewith materials of the first electrode layer and the second electrodelayer. Examples of the configuration of the light-emitting element aredescribed below; it is needless to say that the configuration of thelight-emitting element is not limited to these examples.

<Configuration Example 1 of Light-emitting Element>

An example of a configuration of the light-emitting element isillustrated in FIG. 8A. In the light-emitting element illustrated inFIG. 8A, an EL layer including a light-emitting unit 1103 is providedbetween an anode 1101 and a cathode 1102.

When a voltage higher than the threshold voltage of the light-emittingelement is applied between the anode 1101 and the cathode 1102, holesare injected to the EL layer from the anode 1101 side and electrons areinjected to the EL layer from the cathode 1102 side. The injectedelectrons and holes are recombined in the EL layer, so that alight-emitting substance contained in the EL layer emits light.

In this specification, a layer or a stacked body which includes oneregion where electrons and holes injected from both ends are recombinedis referred to as a light-emitting unit. Therefore, the configurationexample 1 of the light-emitting element includes one light-emittingunit.

The light-emitting unit 1103 includes at least one light-emitting layercontaining a light-emitting substance, and may have a structure in whichthe light-emitting layer and a layer other than the light-emitting layerare stacked. Examples of the layer other than the light-emitting layerare layers containing a substance having a high hole-injection property,a substance having a high hole-transport property, a substance having apoor hole-transport property (substance which blocks holes), a substancehaving a high electron-transport property, a substance having a highelectron-injection property, a substance having a bipolar property(substance having high electron- and hole-transport properties), and thelike.

An example of a specific configuration of the light-emitting unit 1103is illustrated in FIG. 8B. In the light-emitting unit 1103 illustratedin FIG. 8B, a hole-injection layer 1113, a hole-transport layer 1114, alight-emitting layer 1115, an electron-transport layer 1116, and anelectron-injection layer 1117 are stacked in this order from the anode1101 side.

<Configuration Example 2 of Light-Emitting Element>

Another example of the configuration of the light-emitting element isillustrated in FIG. 8C. In the light-emitting element illustrated inFIG. 8C, the EL layer including the light-emitting unit 1103 is providedbetween the anode 1101 and the cathode 1102. Further, an intermediatelayer 1104 is provided between the cathode 1102 and the light-emittingunit 1103. Note that a configuration similar to that of thelight-emitting unit included in the configuration example 1 of thelight-emitting element, which is described above, can be applied to thelight-emitting unit 1103 in the configuration example 2 of thelight-emitting element and that the description of the configurationexample 1 of the light-emitting element can be referred to for thedetails.

The intermediate layer 1104 may be formed to include at least acharge-generation region, and may have a structure in which thecharge-generation region and a layer other than the charge-generationregion are stacked. For example, a structure can be employed in which afirst charge-generation region 1104 c, an electron-relay layer 1104 b,and an electron-injection buffer 1104 a are stacked in this order fromthe cathode 1102 side.

The behaviors of electrons and holes in the intermediate layer 1104 aredescribed. When a voltage higher than the threshold voltage of thelight-emitting element is applied between the anode 1101 and the cathode1102, in the first charge-generation region 1104 c, holes and electronsare generated, and the holes move into the cathode 1102 and theelectrons move into the electron-relay layer 1104 b. The electron-relaylayer 1104 b has a high electron-transport property and immediatelytransfers the electrons generated in the first charge-generation region1104 c to the electron-injection buffer 1104 a. The electron-injectionbuffer 1104 a can lower a barrier against electron injection into thelight-emitting unit 1103, so that the efficiency of the electroninjection into the light-emitting unit 1103 is increased. Thus, theelectrons generated in the first charge-generation region 1104 c areinjected into the LUMO level of the light-emitting unit 1103 through theelectron-relay layer 1104 b and the electron-injection buffer 1104 a.

In addition, the electron-relay layer 1104 b can prevent interaction inwhich the substance included in the first charge-generation region 1104c and the substance included in the electron-injection buffer 1104 areact with each other at the interface therebetween and the functions ofthe first charge-generation region 1104 c and the electron-injectionbuffer 1104 a are impaired.

The range of choices of materials that can be used for the cathode inthe configuration example 2 of the light-emitting element is wider thanthat of materials that can be used for the cathode in the configurationexample 1. This is because the cathode in the configuration example 2should simply receive holes generated by the intermediate layer and amaterial having a relatively high work function can be used for thecathode.

<Configuration Example 3 of Light-Emitting Element>

Another example of the configuration of the light-emitting element isillustrated in FIG. 8D. In the light-emitting element illustrated inFIG. 8D, an EL layer including two light-emitting units is providedbetween the anode 1101 and the cathode 1102. Furthermore, theintermediate layer 1104 is provided between a first light-emitting unit1103 a and a second light-emitting unit 1103 b.

Note that the number of light-emitting units provided between the anodeand the cathode is not limited to two. A light-emitting elementillustrated in FIG. 8E has what is called a tandem structure, that is, astructure in which a plurality of light-emitting units 1103 is stacked.Note that in the case where n (n is a natural number greater than orequal to 2) light-emitting units 1103 are provided between the anode andthe cathode, for example, the intermediate layer 1104 is providedbetween an m-th (m is a natural number greater than or equal to 1 andless than or equal to n−1) light-emitting unit and an (m+1)-thlight-emitting unit.

Note that a configuration similar to that in the configuration example 1of the light-emitting element can be applied to the light-emitting unit1103 in the configuration example 3 of the light-emitting element; aconfiguration similar to that in the configuration example 2 of thelight-emitting element can be applied to the intermediate layer 1104 inthe configuration example 3 of the light-emitting element. Thus, for thedetails, the description of the configuration example 1 of thelight-emitting element or the configuration example 2 of thelight-emitting element can be referred to.

The behaviors of electrons and holes in the intermediate layer 1104provided between the light-emitting units are described. When a voltagehigher than the threshold voltage of the light-emitting element isapplied between the anode 1101 and the cathode 1102, holes and electronsare generated in the intermediate layer 1104, and the holes move intothe light-emitting unit provided on the cathode 1102 side and theelectrons move into the light-emitting unit provided on the anode 1101side. The holes injected into the light-emitting unit provided on thecathode side are recombined with electrons injected from the cathodeside, so that a light-emitting substance contained in the light-emittingunit emits light. The electrons injected into the light-emitting unitprovided on the anode side are recombined with holes injected from theanode side, so that a light-emitting substance contained in thelight-emitting unit emits light. Thus, the holes and electrons generatedin the intermediate layer 1104 cause light emission in differentlight-emitting units.

Note that the light-emitting units can be provided in contact with eachother when these light-emitting units allow the same structure as theintermediate layer to be formed therebetween. Specifically, when onesurface of the light-emitting unit is provided with a charge-generationregion, the charge-generation region functions as a firstcharge-generation region of the intermediate layer; thus, thelight-emitting units can be provided in contact with each other.

The configuration examples 1 to 3 of the light-emitting element can beimplemented in combination. For example, an intermediate layer may beprovided between the cathode and the light-emitting unit in theconfiguration example 3 of the light-emitting element.

Further, a plurality of light-emitting substances which emit light ofdifferent colors can be used, whereby, for example, white light emissioncan also be obtained by expanding the width of the emission spectrum. Inorder to obtain white light emission, for example, a configuration maybe employed in which at least two layers containing light-emittingsubstances are provided so that light of complementary colors isemitted. Specific examples of complementary colors include “blue andyellow”, “blue-green and red”, and the like.

Further, in order to obtain white light emission with an excellent colorrendering property, an emission spectrum preferably spreads through theentire visible light region. For example, a light-emitting element mayinclude layers emitting light of blue, green, and red.

This embodiment can be implemented in an appropriate combination withany of the other embodiments described in this specification.

Embodiment 4

An example of a semiconductor which is preferably used for the regionwhere a channel is formed in the transistor which is shown as an examplein the above embodiment is described below.

An oxide semiconductor has a wide energy gap of 3.0 eV or more. Atransistor including an oxide semiconductor film obtained by processingof the oxide semiconductor in an appropriate condition and a sufficientreduction in carrier density of the oxide semiconductor can have muchlower leakage current between a source and a drain in an off state(off-state current) than a conventional transistor including silicon.

An oxide semiconductor containing at least indium (In) or zinc (Zn) ispreferably used. In particular, In and Zn are preferably contained. Inaddition, as a stabilizer for reducing variation in electricalcharacteristics of a transistor using the oxide semiconductor, one ormore elements selected from gallium (Ga), tin (Sn), hafnium (Hf),zirconium (Zr), titanium (Ti), scandium (Sc), yttrium (Y), and alanthanoid (such as cerium (Ce), neodymium (Nd), or gadolinium (Gd)) ispreferably contained.

As the oxide semiconductor, for example, an indium oxide, a tin oxide, azinc oxide, a two-component metal oxide such as an In—Zn-based oxide, aSn—Zn-based oxide, an Al—Zn-based oxide, a Zn—Mg-based oxide, aSn—Mg-based oxide, an In—Mg-based oxide, or an In—Ga-based oxide, athree-component metal oxide such as an In—Ga—Zn-based oxide (alsoreferred to as IGZO), an In—Al—Zn-based oxide, an In—Sn—Zn-based oxide,a Sn—Ga—Zn-based oxide, an Al—Ga—Zn-based oxide, a Sn—Al—Zn-based oxide,an In—Hf—Zn-based oxide, an In—Zr—Zn-based oxide, an In—Ti—Zn-basedoxide, an In—Sc—Zn-based oxide, an In—Y—Zn-based oxide, anIn—La—Zn-based oxide, an In—Ce—Zn-based oxide, an In—Pr—Zn-based oxide,an In—Nd—Zn-based oxide, an In—Sm—Zn-based oxide, an In—Eu—Zn-basedoxide, an In—Gd—Zn-based oxide, an In—Tb—Zn-based oxide, anIn—Dy—Zn-based oxide, an In—Ho—Zn-based oxide, an In—Er—Zn-based oxide,an In—Tm—Zn-based oxide, an In—Yb—Zn-based oxide, or an In—Lu—Zn-basedoxide, or a four-component metal oxide such as an In—Sn—Ga—Zn-basedoxide, an In—Hf—Ga—Zn-based oxide, an In—Al—Ga—Zn-based oxide, anIn—Sn—Al—Zn-based oxide, an In—Sn—Hf—Zn-based oxide, or anIn—Hf—Al—Zn-based oxide can be used.

Here, an “In—Ga—Zn-based oxide” means an oxide containing In, Ga, and Znas main components and there is no limitation on the ratio of In:Ga:Zn.Further, a metal element in addition to In, Ga, and Zn may be contained.

Alternatively, a material represented by InMO₃(ZnO)_(m) (m>0, where m isnot an integer) may be used as the oxide semiconductor. Note that Mrepresents one or more metal elements selected from Ga, Fe, Mn, and Co,or the above-described element as a stabilizer. Alternatively, amaterial represented by In₂SnO₅(ZnO)_(n) (n>0, where n is an integer)may be used as the oxide semiconductor.

For example, an In—Ga—Zn-based oxide with an atomic ratio ofIn:Ga:Zn=1:1:1, In:Ga:Zn=3:1:2, or In:Ga:Zn=2:1:3, or an oxide with anatomic ratio close to the above atomic ratios can be used.

The oxide semiconductor film may be either single crystal ornon-single-crystal. In the latter case, the oxide semiconductor film maybe either amorphous or polycrystalline. Further, the oxide semiconductorfilm may have either an amorphous structure including a crystallineportion or a non-amorphous structure.

The oxide semiconductor film is preferably a CAAC-OS (c-axis alignedcrystalline oxide semiconductor) film.

The CAAC-OS film is described below.

In most cases, a crystal part of the CAAC-OS film fits inside a cubewhose one side is less than 100 nm. From an observation image obtainedwith a transmission electron microscope (TEM), a boundary between acrystal part and a crystal part in the CAAC-OS film is not clear.Further, with the TEM, a grain boundary in the CAAC-OS film is notfound. Thus, in the CAAC-OS film, a reduction in electron mobility dueto the grain boundary is suppressed.

In each of the crystal parts included in the CAAC-OS film, a c-axis isaligned in a direction parallel to a normal vector of a surface wherethe CAAC-OS film is formed or a normal vector of a surface of theCAAC-OS film, triangular or hexagonal atomic arrangement which is seenfrom the direction perpendicular to the a-b plane is formed, and metalatoms are arranged in a layered manner or metal atoms and oxygen atomsare arranged in a layered manner when seen from the directionperpendicular to the c-axis. Note that, among crystal parts, thedirections of the a-axis and the b-axis of one crystal part may bedifferent from those of another crystal part. In this specification, aterm “perpendicular” includes a range from 80° to 100°. In addition, aterm “parallel” includes a range from −10° to 10°.

In the CAAC-OS film, distribution of crystal parts is not necessarilyuniform. For example, in the formation process of the CAAC-OS film, inthe case where crystal growth occurs from a surface side of the oxidesemiconductor film, the proportion of crystal parts in the vicinity ofthe surface of the oxide semiconductor film is higher than that in thevicinity of the surface where the oxide semiconductor film is Ruined insome cases. Further, when an impurity is added to the CAAC-OS film,crystallinity of the crystal part in a region to which the impurity isadded is lowered in some cases.

Since the c-axes of the crystal parts included in the CAAC-OS film arealigned in the direction parallel to a normal vector of a surface wherethe CAAC-OS film is formed or a normal vector of a surface of theCAAC-OS film, the directions of the c-axes may be different from eachother depending on the shape of the CAAC-OS film (the cross-sectionalshape of the surface where the CAAC-OS film is formed or thecross-sectional shape of the surface of the CAAC-OS film) Note that whenthe CAAC-OS film is formed, the direction of the c-axis of the crystalpart is the direction parallel to a normal vector of the surface wherethe CAAC-OS film is formed or a normal vector of the surface of theCAAC-OS film The crystal part is formed by film formation or byperforming treatment for crystallization such as heat treatment afterfilm formation.

There are three methods for forming a CAAC-OS film when the CAAC-OS filmis used as the oxide semiconductor film.

The first method is to form an oxide semiconductor film at a temperaturehigher than or equal to 100° C. and lower than or equal to 450° C.,whereby crystal parts in which the c-axes are aligned in the directionparallel to a normal vector of a surface where the oxide semiconductorfilm is formed or a normal vector of a surface of the oxidesemiconductor film are formed in the oxide semiconductor film.

The second method is to form an oxide semiconductor film with a smallthickness and then heat it at a temperature higher than or equal to 200°C. and lower than or equal to 700° C., to form, in the oxidesemiconductor film, crystal parts in which the c-axes are aligned in thedirection parallel to a normal vector of a surface where the oxidesemiconductor film is formed or a normal vector of a surface of theoxide semiconductor film.

The third method is to form a first oxide semiconductor film with asmall thickness, then heat it at a temperature higher than or equal to200° C. and lower than or equal to 700° C., and form a second oxidesemiconductor film, whereby crystal parts in which the c-axes arealigned in the direction parallel to a normal vector of a surface wherethe oxide semiconductor film is formed or a normal vector of a surfaceof the oxide semiconductor film are formed in the oxide semiconductorfilm.

In a transistor using the CAAC-OS film, change in electricalcharacteristics due to irradiation with visible light or ultravioletlight is small. Thus, the transistor has high reliability.

The CAAC-OS film is preferably formed by a sputtering method with apolycrystalline oxide semiconductor sputtering target. When ions collidewith the sputtering target, a crystal region included in the sputteringtarget may be separated from the target along an a-b plane; in otherwords, a sputtered particle having a plane parallel to the a-b plane(flat-plate-like sputtered particle or pellet-like sputtered particle)may flake off from the sputtering target. In that case, theflat-plate-like or pellet-like sputtered particle reaches a surfacewhere the CAAC-OS film is formed while maintaining their crystal state,whereby the CAAC-OS film can be formed.

For the deposition of the CAAC-OS film, the following conditions arepreferably used.

By reducing the amount of impurities entering the CAAC-OS film duringthe deposition, the crystal state can be prevented from being broken bythe impurities. For example, the concentration of impurities (e.g.,hydrogen, water, carbon dioxide, or nitrogen) which exist in thedeposition chamber may be reduced. Furthermore, the concentration ofimpurities in a deposition gas may be reduced. Specifically, adeposition gas whose dew point is −80° C. or lower, preferably −100° C.or lower is used.

By increasing the heating temperature of the surface where the CAAC-OSfilm is formed (for example, the substrate heating temperature) duringthe deposition, migration of a sputtered particle is likely to occurafter the sputtered particle reaches the surface where the CAAC-OS filmis formed. Specifically; the temperature of the surface where theCAAC-OS film is formed during the deposition is higher than or equal to100° C. and lower than or equal to 740° C., preferably higher than orequal to 200° C. and lower than or equal to 500° C. By increasing thetemperature of the surface where the CAAC-OS film is formed during thedeposition, when the flat-plate-like or pellet-like sputtered particlereaches the surface where the CAAC-OS film is formed, migration occurson the surface where the CAAC-OS film is formed, so that a flat plane ofthe sputtered particle is attached to the surface where the CAAC-OS filmis formed.

Furthermore, it is preferable that the proportion of oxygen in thedeposition gas be increased and the power be optimized in order toreduce plasma damage at the deposition. The proportion of oxygen in thedeposition gas is 30 vol % or higher, preferably 100 vol %.

As an example of the sputtering target, an In—Ga—Zn—O compound target isdescribed below.

The In—Ga—Zn—O compound target, which is polycrystalline, is made bymixing InO_(X) powder, GaO_(Y) powder, and ZnO_(Z) powder in apredetermined molar ratio, applying pressure, and performing heattreatment at a temperature higher than or equal to 1000° C. and lowerthan or equal to 1500° C. Note that X, Y and Z are given positivenumbers. Here, the predetermined molar ratio of InO_(X) powder toGaO_(Y) powder and ZnO_(Z) powder is, for example, 1:1:1, 1:1:2, 1:3:2,2:1:3, 2:2:1, 3:1:1, 3:1:2, 3:1:4, 4:2:3, 8:4:3, or a ratio close tothese ratios. The kinds of powder and the molar ratio for mixing powdermay be determined as appropriate depending on the desired sputteringtarget.

The above is the description of the CAAC-OS film.

Further, when the oxide semiconductor film contains a large amount ofhydrogen, the hydrogen and an oxide semiconductor are bonded to eachother, so that part of the hydrogen serves as a donor and causesgeneration of an electron which is a carrier. As a result, the thresholdvoltage of the transistor shifts in the negative direction. Accordingly,the concentration of hydrogen in the oxide semiconductor film ispreferably lower than 5×10¹⁸ atoms/cm³, more preferably lower than orequal to 1×10¹⁸ atoms/cm³, still more preferably lower than or equal to5×10¹⁷ atoms/cm³, further more preferably lower than or equal to 1×10¹⁶atoms/cm³. Note that the concentration of hydrogen in the oxidesemiconductor film is measured by secondary ion mass spectrometry(SIMS).

After formation of the oxide semiconductor film, it is preferable thatdehydration treatment (dehydrogenation treatment) be performed to removehydrogen or moisture from the oxide semiconductor film so that the oxidesemiconductor film is highly purified to contain impurities as little aspossible, and that oxygen be added to the oxide semiconductor film tofill oxygen vacancies increased by the dehydration treatment(dehydrogenation treatment). In this specification and the like,supplying oxygen to an oxide semiconductor film may be expressed asoxygen adding treatment, or treatment for making the oxygen content ofan oxide semiconductor film be in excess of that of the stoichiometriccomposition may be expressed as treatment for making an oxygen-excessstate.

In this manner, hydrogen or moisture is removed from the oxidesemiconductor film by the dehydration treatment (dehydrogenationtreatment) and oxygen vacancies therein are filled by the oxygen addingtreatment, whereby the oxide semiconductor film can be turned into ani-type (intrinsic) or substantially i-type oxide semiconductor film Theoxide semiconductor film formed in such a manner includes extremely few(close to zero) carriers derived from a donor, and the carrierconcentration thereof is lower than 1×10¹⁴/cm³, preferably lower than1×10¹²/cm³, further preferably lower than 1×10¹¹/cm³, still furtherpreferably lower than 1.45×10¹⁰/cm³.

The transistor including the oxide semiconductor film which is highlypurified by sufficiently reducing the hydrogen concentration, and inwhich defect levels in the energy gap due to oxygen vacancies arereduced by sufficiently supplying oxygen can achieve excellent off-statecurrent characteristics. For example, the off-state current permicrometer in the channel width with a channel length of 1 μm at roomtemperature (25° C.) is less than or equal to 100 yA (1 yA (yoctoampere)is 1×10⁻²⁴ A), desirably less than or equal to 10 yA. In addition, theoff-state current per micrometer in the channel width at 85° C. is lessthan or equal to 100 zA (1 zA (zeptoampere) is 1×10⁻²¹ A), desirablyless than or equal to 10 zA. In this manner, the transistor which hasextremely favorable off-state current characteristics can be obtainedwith the use of an i-type (intrinsic) or substantially i-type oxidesemiconductor film.

The oxide semiconductor film may have a structure in which a pluralityof oxide semiconductor films is stacked.

For example, the oxide semiconductor film may be a stack of a firstoxide semiconductor film, a second oxide semiconductor film, and a thirdoxide semiconductor film which have different compositions. For example,the following structure can be employed: the first oxide semiconductorfilm and the third oxide semiconductor film are formed using athree-component metal oxide and the second oxide semiconductor film isformed using a two-component metal oxide; or the first oxidesemiconductor film and the third oxide semiconductor film are formedusing a two-component metal oxide and the second oxide semiconductorfilm is formed using a three-component metal oxide.

Further, the constituent elements of the first oxide semiconductor film,the second oxide semiconductor film, and the third oxide semiconductorfilm may be the same and the proportions of the constituent elements ofthe first oxide semiconductor film, the second oxide semiconductor film,and the third oxide semiconductor film may be different. For example,the first oxide semiconductor film and the third oxide semiconductorfilm may each have an atomic ratio of In:Ga:Zn=1:1:1, and the secondoxide semiconductor film may have an atomic ratio of In:Ga:Zn=3:1:2.Alternatively, the first oxide semiconductor film and the third oxidesemiconductor film may each have an atomic ratio of In:Ga:Zn=1:3:2, andthe second oxide semiconductor film may have an atomic ratio ofIn:Ga:Zn=3:1:2.

At this time, the second oxide semiconductor film preferably containsmore In than Ga (In>Ga). Further, the first oxide semiconductor film andthe third oxide semiconductor film preferably contain In and Ga at aproportion of In≦Ga.

In an oxide semiconductor, the s orbital of heavy metal mainlycontributes to carrier conduction, and when the In content in the oxidesemiconductor is increased, overlaps of the s orbitals are likely to beincreased. Therefore, an oxide having a composition of In>Ga has highermobility than an oxide having a composition of In≦Ga. Further, in Ga,the formation energy of an oxygen vacancy is larger and thus oxygenvacancies are less likely to be generated, than in In; therefore, theoxide having a composition of In≦Ga has more stable characteristics thanthe oxide having a composition of In>Ga.

Note that when the film (such as a gate insulating film) which is incontact with and is different from the oxide semiconductor film isformed, an impurity might be diffused into the oxide semiconductor filmfrom the film formed to be in contact with the oxide semiconductor film.When silicon, carbon, or the like is diffused into the oxidesemiconductor film, electrical characteristics of the transistor may beadversely affected.

However, the adverse effect on the electrical characteristics of thetransistor (e.g., a reduction in mobility) which is attributed toimpurity diffusion can be reduced when a stacked-layer structure of theoxide semiconductor films is provided as described above and the oxidesemiconductor film (i.e., the oxide semiconductor film having acomposition of In≦Ga, corresponding to the first oxide semiconductorfilm and the third oxide semiconductor film described above) which hasfewer oxygen vacancies and more stable characteristics than the oxidesemiconductor film that has high mobility (i.e., the oxide semiconductorfilm having a composition of In>Ga, corresponding to the second oxidesemiconductor film described above) is provided in contact with theoxide semiconductor film that has high mobility, whereby the oxidesemiconductor film that has high mobility is not in contact with a filmwhich is in contact with the oxide semiconductor film. In this manner,the mobility and reliability of the transistor can be improved.

This embodiment can be implemented in an appropriate combination withany of the other embodiments described in this specification.

Embodiment 5

In this embodiment, examples of electronic devices each including adisplay device with a touch sensor in one embodiment of the presentinvention will be described with reference to FIGS. 9A to 9D.

An electronic device illustrated in FIG. 9A is an example of a portableinformation terminal.

The electronic device illustrated in FIG. 9A has a housing 1011 which isprovided with a panel 1012, a button 1013, and a speaker 1014.

Note that the housing 1011 may be provided with a connection terminalfor connecting the electronic device to an external device and a buttonfor operating the electronic device.

The button 1013 is provided on the housing 1011. When the button 1013 isa power button, for example, the electronic device can be turned on oroff by pressing the button 1013.

The speaker 1014 is provided on the housing 1011. The speaker 1014outputs sound.

Note that the housing 1011 may be provided with a microphone, in whichcase the electronic device in FIG. 9A can function as a telephone, forexample.

The electronic device illustrated in FIG. 9A functions as at least oneof a telephone, an e-book reader, a personal computer, and a gamemachine, for example.

In the panel 1012, the display device with a touch sensor in oneembodiment of the present invention can be used.

An electronic device illustrated in FIG. 9B is an example of a foldableinformation terminal.

The electronic device illustrated in FIG. 9B has a housing 1021 aprovided with a panel 1022 a, a housing 1021 b provided with a panel1022 b, a hinge 1023, a button 1024, a connection terminal 1025, arecording media inserting portion 1026, and a speaker 1027.

The housing 1021 a and the housing 1021 b are connected by the hinge1023.

Since the electronic device in FIG. 9B includes the hinge 1023, it canbe folded so that the panels 1022 a and 1022 b face each other.

The button 1024 is provided on the housing 1021 b. Note that the button1024 may be provided on the housing 1021 a. For example, when the button1024 having a function as a power button is provided, supply of powersupply voltage to the electronic device can be controlled by pressingthe button 1024.

The connection terminal 1025 is provided on the housing 1021 a. Notethat the connection terminal 1025 may be provided on the housing 1021 b.Alternatively, a plurality of connection terminals 1025 may be providedon one or both of the housings 1021 a and 1021 b. The connectionterminal 1025 is a terminal for connecting the electronic deviceillustrated in FIG. 9B to another device.

The recording media inserting portion 1026 is provided on the housing1021 a. The recording media inserting portion 1026 may be provided onthe housing 1021 b. Alternatively, a plurality of recording mediainserting portions 1026 may be provided on one or both of the housings1021 a and 1021 b. For example, a card-type recording medium is insertedinto the recording media inserting portion so that data can be read tothe electronic device from the card-type recording medium or data storedin the electronic device can be written to the card-type recordingmedium.

The speaker 1027 is provided on the housing 1021 b. The speaker 1027outputs sound. Note that the speaker 1027 may be provided on the housing1021 a.

Note that the housing 1021 a or the housing 1021 b may be provided witha microphone, in which case the electronic device in FIG. 9B canfunction as a telephone, for example.

The electronic device illustrated in FIG. 9B functions as at least oneof a telephone, an e-book reader, a personal computer, and a gamemachine, for example.

In the panels 1022 a and the panel 1022 b, the display device with atouch sensor in one embodiment of the present invention can be used.

An electronic device illustrated in FIG. 9C is an example of astationary information terminal. The electronic device illustrated inFIG. 9C has a housing 1031 which is provided with a panel 1032, a button1033, and a speaker 1034.

Note that a panel similar to the panel 1032 may be provided on a topboard 1035 of the housing 1031.

Further, the housing 1031 may be provided with a ticket slot for issuinga ticket or the like, a coin slot, a bill slot, and/or the like.

The button 1033 is provided on the housing 1031. For example, when thebutton 1033 is a power button, supply of a power voltage to theelectronic device can be controlled by pressing the button 1033.

The speaker 1034 is provided on the housing 1031. The speaker 1034outputs sound.

The electronic device in FIG. 9C serves as an automated teller machine,an information communication terminal (also referred to as multimediastation) for ordering a ticket or the like, or a game machine, forexample.

In the panel 1032, the display device with a touch sensor in oneembodiment of the present invention can be used.

FIG. 9D illustrates an example of a stationary information terminal. Theelectronic device in FIG. 9D has a housing 1041 provided with a panel1042, a support 1043 for supporting the housing 1041, a button 1044, aconnection terminal 1045, and a speaker 1046.

Note that besides the connection terminal 1045, the housing 1041 may beprovided with another connection terminal for connecting the electronicdevice to an external device.

The button 1044 is provided on the housing 1041. For example, when thebutton 1044 is a power button, supply of a power voltage to theelectronic device can be controlled by pressing the button 1044.

The connection terminal 1045 is provided on the housing 1041. Theconnection terminal 1045 is a terminal for connecting the electronicdevice in FIG. 9D to another device. For example, when the electronicdevice in FIG. 9D and a personal computer are connected with theconnection terminal 1045, the panel 1042 can display an imagecorresponding to a data signal input from the personal computer. Forexample, when the panel 1042 of the electronic device in FIG. 9D islarger than a panel of another electronic device connected thereto, adisplayed image of the other electronic device can be enlarged, so thata plurality of viewers can easily see the image at the same time.

The speaker 1046 is provided on the housing 1041. The speaker 1046outputs sound.

The electronic device in FIG. 9D functions as at least one of an outputmonitor, a personal computer, and a television set, for example.

In the panel 1042, the display device with a touch sensor in oneembodiment of the present invention can be used.

The above is the description of the electronic devices illustrated inFIGS. 9A to 9D.

As described with reference to FIGS. 9A to 9D, the display device with atouch sensor in one embodiment of the present invention is used in thepanel of each electronic device in this embodiment. Thus, the weight,size, and thickness of the electronic device can be decreased.

The display device in one embodiment of the present invention can alsohave flexibility because of its very small total thickness. Accordingly,the electronic device can also include a panel having a curved surfaceor a panel which can be curved.

This embodiment can be implemented in an appropriate combination withany of the other embodiments described in this specification.

This application is based on Japanese Patent Application serial no.2012-156357 filed with Japan Patent Office on Jul. 12, 2012, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A display device comprising: a first substrate; afirst layer over the first substrate, the first layer including alight-emitting element; a first conductive layer over the firstsubstrate; a second substrate over the first conductive layer, thesecond substrate being provided with a second layer including a touchsensor; and a second conductive layer under the second substrate, thesecond conductive layer being electrically connected to the touchsensor, wherein the first substrate and the second substrate areattached to each other with an adhesive layer so that the first layerand the second layer are interposed between the first substrate and thesecond substrate, wherein the first conductive layer is electricallyconnected to the second conductive layer through a conductive connector,and wherein each of the first substrate and the second substrate is aglass substrate.
 2. The display device according to claim 1, furthercomprising a third layer including a color filter overlapping with thesecond layer.
 3. The display device according to claim 1, wherein theadhesive layer is provided between the conductive connector and thelight-emitting element, wherein the adhesive layer is provided so as tosurround the light-emitting element, and wherein the first conductivelayer and the second conductive layer are electrically connected to eachother outside a region surrounded by the adhesive layer.
 4. The displaydevice according to claim 1, wherein the adhesive layer contains a glassmaterial.
 5. The display device according to claim 1, wherein the firstlayer further comprises a transistor being electrically connected to thelight-emitting element, and wherein the transistor comprises an oxidesemiconductor in a channel formation region.
 6. The display deviceaccording to claim 1, further comprising: a first connection terminalover the first substrate, the first connection terminal beingelectrically connected to the first layer; a second connection terminalover the first substrate, the second connection terminal beingelectrically connected to the first conductive layer; a flexible printedcircuit being electrically connected to each of the first connectionterminal and the second connection terminal; and a reinforcing materialbeing in contact with the flexible printed circuit and the secondsubstrate, wherein each of the first connection terminal and the secondconnection terminal does not overlap with the second substrate.
 7. Thedisplay device according to claim 1, wherein each of the first substrateand the second substrate has a thickness of 10 μm to 200 μm.
 8. A modulecomprising the display device according to claim
 1. 9. An electronicdevice comprising the display device according to claim
 1. 10. A methodfor manufacturing a display device, comprising the steps of: attaching afirst substrate which is fixed over a first support substrate andprovided with a first layer including a touch sensor over the firstsubstrate and a second substrate which is fixed over a second supportsubstrate and provided with a second layer over the second substrate toeach other with a first adhesive layer so that the first layer and thesecond layer are interposed between the first substrate and the secondsubstrate; separating the first substrate and the first supportsubstrate from each other; and separating the second substrate and thesecond support substrate from each other, wherein the first layerincludes a first conductive layer, and the second layer includes asecond conductive layer, and wherein the first conductive layer iselectrically connected to the second conductive layer through aconductive connector between the first conductive layer and the secondconductive layer after the attaching step.
 11. The method formanufacturing a display device according to claim 10, further comprisingthe steps of: attaching the second substrate which is fixed over thesecond support substrate and provided with the second layer including alight-emitting element over the second substrate and a third substratewhich is fixed over a third support substrate and provided with a thirdlayer including a color filter over the third substrate to each otherwith a second adhesive layer so that the second layer and the thirdlayer are interposed between the second substrate and the thirdsubstrate; and separating the third substrate and the third supportsubstrate from each other before the attaching step of the firstsubstrate and the second substrate, wherein the attaching step of thesecond substrate and the third substrate is performed before theattaching step of the first substrate and the second substrate, andwherein the first substrate is fixed to the second substrate with thethird substrate and the third layer interposed therebetween in theattaching step of the first substrate and the second substrate.
 12. Themethod for manufacturing a display device according to claim 10, furthercomprising the steps of: attaching the second substrate which is fixedover the second support substrate and provided with the second layerincluding a color filter over the second substrate and a third substratewhich is fixed over a third support substrate and provided with a thirdlayer including a light-emitting element over the third substrate toeach other with a second adhesive layer so that the second layer and thethird layer are interposed between the second substrate and the thirdsubstrate; and separating the third substrate and the third supportsubstrate from each other before the attaching step of the firstsubstrate and the second substrate, wherein the attaching step of thesecond substrate and the third substrate is performed before theattaching step of the first substrate and the second substrate, andwherein the first substrate is fixed to the second substrate with thethird substrate and the third layer interposed therebetween in theattaching step of the first substrate and the second substrate.
 13. Themethod for manufacturing a display device according to claim 10, whereinthe first layer is a stack of the touch sensor and a third layerincluding a color filter layer, and wherein the second layer includes alight-emitting element.
 14. The method for manufacturing a displaydevice according to claim 10, wherein a surface of the first substrate,which is fixed to the first support substrate, has a roughness of 2 nmor less.
 15. The method for manufacturing a display device according toclaim 10, wherein the first substrate is a glass substrate having athickness of 10 μm to 200 μm, and wherein the glass substrate is fixedto the first support substrate with a resin containing an organiccompound or a silicon compound.
 16. The method for manufacturing adisplay device according to claim 10, wherein the first substrate is aglass substrate having a thickness of 10 μm to 200 μm, wherein thesecond substrate is a glass substrate having a thickness of 10 μm to 200μm, wherein the first support substrate is thicker than the firstsubstrate, and wherein the second support substrate is thicker than thesecond substrate.
 17. The method for manufacturing a display deviceaccording to claim 10, wherein the first substrate and the secondsubstrate are directly attached to each other with the first adhesivelayer by the attaching step of the first substrate and the secondsubstrate.
 18. A method for manufacturing a display device, comprisingthe steps of: attaching a first substrate which is fixed over a firstsupport substrate and provided with a first layer including a touchsensor over the first substrate and a second substrate which is fixedover a second support substrate and provided with a second layer overthe second substrate to each other with a first adhesive layer so thatthe first layer and the second layer are interposed between the firstsubstrate and the second substrate; separating the first substrate andthe first support substrate from each other; and separating the secondsubstrate and the second support substrate from each other.
 19. Themethod for manufacturing a display device according to claim 18, whereina surface of the first substrate, which is fixed to the first supportsubstrate, has a roughness of 2 nm or less.
 20. The method formanufacturing a display device according to claim 18, wherein the firstsubstrate is a glass substrate having a thickness of 10 μm to 200 μm,and wherein the glass substrate is fixed to the first support substratewith a resin containing an organic compound or a silicon compound. 21.The method for manufacturing a display device according to claim 18,wherein the first substrate is a glass substrate having a thickness of10 μm to 200 μm, wherein the second substrate is a glass substratehaving a thickness of 10 μm to 200 μm, wherein the first supportsubstrate is thicker than the first substrate, and wherein the secondsupport substrate is thicker than the second substrate.
 22. The methodfor manufacturing a display device according to claim 18, wherein thefirst substrate and the second substrate are directly attached to eachother with the first adhesive layer by the attaching step of the firstsubstrate and the second substrate.